Anatomy and physiology of pregnancy

Anatomy and physiology of pregnancy. Mathernal and fetal nutrition.

Prepared by assistant professor N.Petrenko, MD, PhD

LEARNING OBJECTIVES

* Determine gravidity and parity using the fiveand four-digit systems.

* Describe the various types of pregnancy tests.

* Explain the expected maternal anatomic and physiologic adaptations to pregnancy.

* Differentiate among presumptive, probable, and positive signs of pregnancy.

* Identify the maternal hormones produced during pregnancy, their target organs, and their major effects on pregnancy.

* Compare the characteristics of the abdomen, vulva, and cervix of the nullipara and multipara.

* Explain recommended maternal weight gain during pregnancy.

* Compare the recommended level of intake of energy sources, protein, and key vitamins and minerals during pregnancy and lactation.

* Give examples of the food sources that provide the nutrients required for optimal maternal nutrition during pregnancy and lactation.

* Examine the role of nutrition supplements during pregnancy.

* List five nutritional risk factors during pregnancy.

* Compare the dietary needs of adolescent and mature pregnant women.

* Give examples of cultural food patterns and possible dietary problems for two ethnic groups or for two alternative eating patterns.

 

KEY TERMS AND DEFINITIONS

ballottement Diagnostic technique using palpation:  a floating fetus, when tapped or pushed, moves away and then returns to touch the examiner's hand

Braxton Hicks sign Mild, intermittent, painless uterine contractions that occur during pregnancy; occur more frequently as pregnancy advances but do not represent true labor; however, they should be distinguished from preterm labor

carpal tunnel syndrome Pressure on the median nerve at the point at which it goes through the carpal tunnel of the wrist; causes soreness, tenderness, and weakness of the muscles of the thumb

Chadwick sign Violet color of vaginal mucous membrane that is visible from approximately the fourth week of pregnancy; caused by increased vascularity

chloasma Increased pigmentation over bridge of nose and cheeks of pregnant women and some women taking oral contraceptives; also known as "mask of pregnancy"

colostrum Fluid in the acini cells of the breasts present from early pregnancy into the early postpartal period; rich in antibodies, which provide protection to the breastfed newborn from many diseases; high in protein, which binds bilirubin; and laxative acting, which speeds the elimination of meconium and helps loosen mucus

diastasis recti abdominis Separation of the two rectus muscles along the median line of the abdominal wall; often seen in women with repeated childbirths or with a multiple gestation (e.g., triplets)

epulis Tumorlike benign lesion of the gingiva seen in pregnant women

funic souffle Soft, muffled, blowing sound produced by blood rushing through the umbilical vessels and synchronous with the fetal heart sounds

Goodell sign Softening of the cervix, a probable sign of pregnancy, occurring during the second month

Hegar sign Softening of the lower uterine segment that is classified as a probable sign of pregnancy, may be present during the second and third months of pregnancy, and is palpated during bimanual examination

human chorionic gonadotropin (hCG) Hormone that is produced by chorionic villi; the biologic marker in pregnancy tests

leukorrhea White or yellowish mucus discharge from the cervical canal or the vagina that may be normal physiologically or caused by pathologic states of the vagina and endocervix

lightening Sensation of decreased abdominal distention produced by uterine descent into the pelvic cavity as the fetal presenting part settles into the pelvis; usually occurs 2 weeks before the onset of labor in nulliparas

linea nigra Line of darker pigmentation seen in some women during the latter part of pregnancy that appears on the middle of the abdomen and extends from the symphysis pubis toward the umbilicus

Montgomery tubercles Small, nodular prominences (sebaceous glands) on the areolas around the nipples of the breasts that enlarge during pregnancy and lactation

operculum Plug of mucus that fills the cervical canal during pregnancy

palmar erythema Rash on the surface of the palms sometimes seen in pregnancy

ptyalism Excessive salivation

pyrosis Burning sensation in the epigastric and sternal region from stomach acid (heartburn)

quickening Maternal perception of fetal movement; usually occurs between weeks 16 and 20 of gestation

striae gravidarum "Stretch marks"; shining reddish lines caused by stretching of the skin, often found on the abdomen, thighs, and breasts during pregnancy; these streaks turn to a fine pinkish white or silver tone in time in fair-skinned women and brownish in darker-skinned women

uterine souffle Soft, blowing sound made by the blood in the arteries of the pregnant uterus and synchronous with the maternal pulse

 

The goal of maternity care is a healthy pregnancy with a physically safe and emotionally satisfying outcome for mother, infant, and family. Consistent health supervision and surveillance are of utmost importance in achieving this outcome. However, many maternal adaptations are unfamiliar to pregnant women and their families. Helping the pregnant woman recognize the relationship between her physical status and the plan for her care assists her in making decisions and encourages her to participate in her own care.

 

GRAVIDITY AND PARITY

An understanding of the following terms used to describe pregnancy and the pregnant woman is essential to the study of maternity care:

• Gravida—a woman who is pregnant

• Gravidity—pregnancy

• Multigravida—a woman who has had two or more pregnancies

• Multipara—a woman who has completed two or more pregnancies to the stage of fetal viability

• Nulligravida—a woman who has never been pregnant

• Nullipara—a woman who has not completed a pregnancy with a fetus or fetuses who have reached the stage of fetal viability

• Parity—the number of pregnancies in which the fetus or fetuses have reached viability, not the number of fetuses (e.g., twins) born; whether the fetus is born alive or is stillborn (fetus who shows no signs of life at birth) after viability is reached does not affect parity

• Postdate or postterm—a pregnancy that goes beyond 42 weeks of gestation

• Preterm—a pregnancy that has reached 20 weeks of gestation but before completion of 37 weeks of gestation

• Primigravida—a woman who is pregnant for the first time

• Primipara—a woman who has completed one pregnancy with a fetus or fetuses who have reached the stage of fetal viability

• Term—a pregnancy from the beginning of the thirtyeighth week of gestation to the end of the forty-second week of gestation

• Viability—capacity to live outside the uterus; approximately 22 to 24 weeks since last menstrual period, or weight of fetus is greater than 500 g

 

Gravidity and parity information is obtained during history-taking interviews and may be recorded in patient records in several ways. One abbreviation commonly used in maternity centers consists of five digits separated with hyphens. The first digit represents the total number of pregnancies, including the present one (gravidity); the second digit represents the total number of term births; the third indicates the number of preterm births; the fourth identifies the number of abortions (miscarriage or elective termination of pregnancy before viability); and the fifth is the number of children currently living. The acronym GTPAL (gravidity, term, preterm, abortions, living children) may be helpful in remembering this system of notation. For example, if a woman pregnant only once with twins gives birth at the thirty-fifth week and the babies survive, the abbreviation that represents this information is "1-0-1-0-2." During her next pregnancy the abbreviation is "2-0-1-0-2." Additional examples are given in Table 1.

Others prefer a four-digit system. The first digit of the five-digit system, which signifies gravidity, is dropped. The acronym TPAL may be useful in remembering what the four digits stand for.

 

Table 1 Gravidity and Parity Using  Five-Digit (GTPAL) System
	GRAVIDITY PREGNANCIES	TERM BIRTH	PRETERM BIRTH	ABORTIONS	LIVING CHILDREN
Sarah is pregnant for the first time.	1	0	0	0	0
She carries the pregnancy to term, and the neonate survives.	1	1	0	0	1
She is pregnant again.	2	1	0	0	1
Her second pregnancy ends in abortion.	2	1	0	1	1
During her third pregnancy, she gives birth to preterm twins.	3	1	1	1	3

 

PREGNANCY TESTS

Early detection of pregnancy allows for early initiation of care. Human chorionic gonadotropin (hCG) is the biologic marker on which pregnancy tests are based. Production of hCG begins as early as the day of implantation and can be detected in the blood as early as 6 days after conception, or approximately 20 days since the last menstrual period (LMP), and in urine approximately 26 days after conception (Cunningham et al., 2001). The level of hCG rises until it peaks at approximately 60 to 70 days of gestation and then begins to decline. The lowest level is reached between 100 and 130 days of pregnancy and remains constant until birth (Varney, 1997).

Serum and urine pregnancy tests are performed in clinics, offices, women's health centers, and laboratory settings. Both serum and urine tests provide accurate results. A 7- to 10-ml sample of venous blood is collected for serum testing. Most urine tests require a first-voided morning urine specimen because it contains levels of hCG approximately the same as those in serum. Random urine samples usually have lower levels. Urine tests are less expensive and provide more immediate results than serum tests (Hatcher et al., 1998).

Many different pregnancy tests are available, but they all depend on recognition of hCG or a beta subunit of hCG. The wide variety of tests precludes discussion of each; however, several categories of tests are described here. The nurse should read the manufacturer's directions for the test to be used.

Immunoassoys, or agglutination inhibition tests, depend on an antigen-antibody reaction between hCG and an antiserum. Usually, the antiserum is mixed with urine, and hCG-coated particles (e.g., latex or blood cells) are added. If hCG is present in the urine, agglutination does not occur because the hCG neutralizes the hCG antibody, and the test is considered positive (Cunningham et al., 2001). Although immunologic tests are accurate from 4 to 10 days after a missed period, they are most appropriate for confirming a pregnancy at or after the sixth week of gestation (Hatcher et al., 1998).

Radioimmunoassay pregnancy tests for the beta subunit of hCG in serum or urine samples use radioactively labeled markers and are usually performed in a laboratory. These tests are accurate with low hCG levels and can confirm pregnancy 1 week after conception (Hatcher et al., 1998).

Radioreceptor assay is a serum test that measures the ability of a blood sample to inhibit the binding of radiolabeled hCG to receptors. The test is 90% to 95% accurate from 6 to 10 days after conception (Pagana & Pagana, 2001).

Enzyme-linked immunosorbent assay (ELISA) testing is the most popular method of testing for pregnancy. It uses a specific monoclonal antibody (anti-hCG) with enzymes to bond with hCG in urine. Depending on the specific test, levels of hCG as low as 5 to 50 mlU/ml can be detected as early as 4 days after implantation (Hatcher et al., 1998). As an office or home procedure it requires minimal time and offers results in 5 minutes. A positive test is indicated by a simple color-change reaction.

ELISA technology is the basis for most over-thecounter home pregnancy tests. With these one-step tests, the woman usually applies urine to a strip and reads the results. The test kits come with directions for collection of the specimen, the testing procedure, and reading of the results. Most manufacturers of the kits provide a toll-free telephone number to call if users have concerns and questions about test procedures or results (see Teaching Guidelines box). The most common error in performing home pregnancy tests is doing the test too early in pregnancy (Hatcher et al., 1998).

 

TEACHING GUIDELINES Home Pregnancy Testing • Follow the manufacturer's instructions carefully. Do not omit steps. • Review the manufacturer's list of foods, medications, and other substances that can affect the test results. • Use a first-voided morning urine specimen. • If the test done at the time of your missed period is negative, repeat the test in 1 week if you still have not had a period. • If you have questions about the test, contact the manufacturer. • Contact your health care provider for follow-up if the test is positive or if the test is negative and you still have not had a period

 

Interpreting the results of pregnancy tests requires some judgment. The type of pregnancy test and its degree of sensitivity (ability to detect low levels of a substance) and specificity (ability to discern the absence of a substance) have to be considered in conjunction with the woman's history. This includes the date of her last normal menstrual period (LNMP), her usual cycle length, and results of previous pregnancy tests. It is important to know if the woman is a substance abuser and what medications she is taking, because medications such as anticonvulsants and tranquilizers can cause false-positive results and diuretics and promethazine can cause false-negative results (Pagana & Pagana, 2001). Improper collection of the specimen, hormone-producing tumors, and laboratory errors also may cause false results. Whenever there is any question, further evaluation or retesting may be appropriate.

ADAPTATIONS TO PREGNANCY

Maternal physiologic adaptations are attributed to the hormones of pregnancy and to mechanical pressures arising from the enlarging uterus and other tissues. These adaptations protect the woman's normal physiologic functioning, meet the metabolic demands pregnancy imposes on her body, and provide a nurturing environment for fetal development and growth. Although pregnancy is a normal phenomenon, problems can occur.

 

SIGNS OF PREGNANCY

Some of the physiologic adaptations are recognized as signs and symptoms of pregnancy. Three commonly used categories ofsigns and symptoms of pregnancy are presumptive, those changes felt by the woman (e.g., amenorrhea, fatigue, nausea and vomiting, breast changes);probable, those changes observed by an examiner (e.g., Hegar sign, ballottement, pregnancy tests); and positive, those signs that are attributed only to the presence of the fetus (e.g., hearing fetal heart tones, visualization of the fetus, and palpating fetal movements). Table 2 summarizes the signs of pregnancy in relation to when they might occur and other causes for their occurrence.

 

Table 2 Sign and Pregnancy
TIME OF OCCURRENCE (GESTATIONAL AGE)	SIGN	OTHER POSSIBLE CAUSE
PRESUMPTIVE SIGNS
3-4 wk	Breast changes	Premenstrual changes, oral contraceptives
4 wk	Amenorrhea	Stress, vigorous exercise, early menopause, endocrine problems, malnutrition
4-14 wk	Nausea, vomiting	Gastrointestinal virus, food poisoning
6-12 wk	Urinary frequency	Infection, pelvic tumors
12 wk	Fatigue	Stress, illness
16-20 wk	Quickening	Gas, peristalsis
PROBABLE SIGNS
5 wk	Goodell sign	Pelvic congestion
6-8 wk	Chadwick sign	Pelvic congestion
6-12 wk	Hegar sign	Pelvic congestion
4-12 wk	Positive pregnancy test (serum)	Hydatidiform mole, choriocarcinoma
6-12 wk	Positive result to pregnancy test (urine)	False-positive results may be caused by pelvic infection, tumors
16 wk	Braxton Hicks contractions	Myomas, other tumors
16-28 wk	Ballottement	Tumors, cervical polyps
POSITIVE SIGNS
5-6 wk	Visualization of fetus by real-time ultrasound examination	No other causes
16wk	Visualization of fetus by x-ray study
6 wk	Fetal heart tones detected by ultrasound examination
8-17 wk	Fetal heart tones detected by Doppler ultrasound stethoscope
17-19 wk	Fetal heart tones detected by fetal Stethoscope
19-22 wk	Fetal movements palpated
Late pregnancy	Fetal movements visible

 

REPRODUCTIVE SYSTEM AND BREASTS

Uterus

The phenomenal uterine growth in the first trimester is stimulated by high levels of estrogen and progesterone. Early uterine enlargement results from increased vascularity and dilation of blood vessels, hyperplasia (production of new muscle fibers and fibroelastic tissue) and hypertrophy (enlargement of preexisting muscle fibers and fibroelastic tissue), and development of the decidua. By 7 weeks of gestation, the uterus is the size of a large hen's egg; by 10 weeks of gestation, it is the size of an orange (twice its nonpregnant size); and by 12 weeks of gestation, it is the size of a grapefruit. After the third month, uterine enlargement is primarily the result of mechanical pressure of the growing fetus (Varney, 1997).

As the uterus enlarges, it also changes in shape and position. At conception the uterus is shaped like an upsidedown pear. During the second trimester, as the muscular walls strengthen and become more elastic, the uterus becomes spherical or globular. Later, as the fetus lengthens, the uterus becomes larger and more ovoid and rises out of the pelvis into the abdominal cavity.

The pregnancy may "show" after the fourteenth week, although this depends to some degree on the woman's height and weight. Abdominal enlargement may be less apparent in the nulipara with good abdominal muscle tone (Fig. 1). Posture also influences the type and degree of abdominal enlargement that occurs. In normal pregnancies the uterus enlarges at a predictable rate. As the uterus grows, it may be palpated above the symphysis pubis some time between the twelfth and fourteenth weeks of pregnancy (Fig. 2). The uterus rises gradually to the level of the umbilicus at 22 to 24 weeks of gestation and nearly reaches the xiphoid process at term. Between weeks 38 and 40, fundal height drops as the fetus begins to descend and engage in the pelvis (lightening) (Fig. 2, dashed line). Generally, lightening occurs in the nullipara approximately 2 weeks before the onset of labor and at the start of labor in the multipara.

 

Fig. 1 Comparison of abdomen, vulva, and cervix in nullipara

(A) and multipara (B) at the same stage of pregnancy.

 

 

Fig. 2 Height of fundus by weeks of normal gestation with a single fetus. Dashed line indicates height after lightening. (From Seidel, H. et al. [1999]. Mosby's guide to physical examination [4th ed.]. St. Louis: Mosby.)

 

Uterine enlargement is determined by measuring fundal height, a measurement commonly used to estimate the duration of pregnancy. However, variation in the position of the fundus or the fetus, variations in the amount of amniotic fluid present, the presence of more than one fetus, maternal obesity, and variation in examiner techniques can reduce the accuracy of this estimation of the duration of pregnancy.

The uterus normally rotates to the right as it elevates, probably because of the presence of the rectosigmoid colon on the left side. However, the extensive hypertrophy (enlargement) of the round ligaments keeps the uterus in the midline. Eventually, the growing uterus touches the anterior abdominal wall and displaces the intestines to either side of the abdomen (Fig. 3). When a pregnant woman is standing, most of her uterus rests against the anterior abdominal wall, and this contributes to altering her center of gravity.

 

 

Fig. 3 Displacement of internal abdominal structures and diaphragm by the enlarging uterus at 4, 6, and 9 months of gestation.

 

At approximately 6 weeks of gestation, softening and compressibility of the lower uterine segment (the uterine isthmus) occur (Hegar sign). This results in exaggerated uterine anteflexion during the first 3 months of pregnancy (Fig. 4). In this position the uterine fundus presses on the urinary bladder, causing the woman to experience urinary frequency.

 

Fig. 4 Hegar sign. Bimanual examination for assessing compressibility, softening of isthmus (lower uterine segment) while the cervix is still firm.

 

Early uterine enlargement may not be symmetric, depending on the site of implantation. For example, if corneal implantation occurred, a soft, irregular bulge (Piskacek sign) may be detected during a pelvic examination (Varney, 1997).

Changes in contractility. Soon after the fourth month of pregnancy, uterine contractions can be felt through the abdominal wall. These contractions are referred to as the Braxton Hicks sign. Braxton Hicks contractions are irregular, painless contractions that occur intermittently throughout pregnancy. These contractions facilitate uterine blood flow through the intervillous spaces of the placenta and thereby promote oxygen delivery to the fetus. Although Braxton Hicks contractions are not painful, some women do complain that they are annoying. After the twenty-eighth week, these contractions become much more definite, but they usually cease with walking or exercise. Braxton Hicks contractions can be mistaken for preterm and true labor; however, they do not increase in intensity or frequency or cause cervical dilation.

Uteroplacental blood flow. Placental perfusion depends on the maternal blood flow to the uterus. Blood flow increases rapidly as the uterus increases in size. Although uterine blood flow increases twentyfold, the fetoplacental unit grows more rapidly. Consequently, more oxygen is extracted from the uterine blood during the latter part of pregnancy (Cunningham et al., 2001). In a normal term pregnancy, one sixth of the total maternal blood volume is within the uterine vascular system. The rate of blood flow through the uterus averages 500 ml/min, and oxygen consumption of the gravid uterus increases to meet fetal needs. A low maternal arterial pressure, contractions of the uterus, and maternal supine position are three factors known to decrease blood flow. Estrogen stimulation may increase uterine blood flow. Doppler ultrasound can be used to measure uterine blood flow velocity, especially in pregnancies at risk because of conditions associated with decreased placental perfusion such as hypertension, intrauterine growth restriction, diabetes mellitus, and multiple gestation (Creasy & Resnik, 1999). Using an ultrasound device or a fetal stethoscope, the health care provider may hear the uterine soufflé or the funic souffle.

Cervical changes. A softening of the cervical tip called Goodell sign may be observed at approximately the beginning of the sixth week in a normal, unscarred cervix. This sign is brought about by increased vascularity, slight hypertrophy, and hyperplasia (increase in number of cells) of the muscle and its collagen-rich connective tissue, which becomes loose, edematous, highly elastic, and increased in volume. The glands near the external os proliferate beneath the stratified squamous epithelium, giving the cervix the velvety appearance characteristic of pregnancy. Friability is increased and may cause slight bleeding after coitus with deep penetration or after vaginal examination. Pregnancy can also cause the squamocolumnar junction, the site for obtaining cells for cervical cancer screening, to be located away from the cervix. Because of all these changes, evaluation of abnormal Papanicolaou tests during pregnancy can be complicated. However, careful assessment of all pregnant women is important because approximately 3% of all cervical cancers are diagnosed during pregnancy (Creasy & Resnik, 1999).

The cervix of the nullipara is rounded. Lacerations of the cervix almost always occur during the birth process. With or without lacerations, however, after childbirth the cervix becomes more oval in the horizontal plane, and the external os appears as a transverse slit (see Fig. 1).

Changes related to the presence of the fetus. Passive movement of the unengaged fetus is called ballottement and can be identified generally between the sixteenth and eighteenth week. Ballottement is a technique of palpating a floating structure by bouncing it gently and feeling it rebound. In the technique used to palpate the fetus, the examiner places a finger in the vagina and taps gently upward, causing the fetus to rise. The fetus then sinks, and a gentle tap is felt on the finger (Fig. 5).

 

Fig. 5 Internal ballottement (18 weeks).

 

The first recognition of fetal movements, or "feeling life," by the multiparous woman may occur as early as the fourteenth to sixteenth week. The nulliparous woman may not notice these sensations until the eighteenth week or later. Quickening is commonly described as a flutter and is difficult to distinguish from peristalsis. Gradually, fetal movements increase in intensity and frequency. The week when quickening occurs provides a tentative clue in dating the duration of gestation.

 

Vagina and vulva

Pregnancy hormones prepare the vagina for stretching during labor and birth by causing the vaginal mucosa to thicken, connective tissue to loosen, smooth muscle to hypertrophy, and the vaginal vault to lengthen. Increased vascularity results in a violet-bluish color of the vaginal mucosa and cervix. The deepened color, termed Chadwick sign, may be evident as early as the sixth week, but is easily noted at the eighth week of pregnancy (Creasy & Resnik, 1999).

Leukorrhea is a white or slightly gray mucoid discharge with a faint musty odor. This copious mucoid fluid occurs in response to cervical stimulation by estrogen and progesterone. The fluid is whitish because of the presence of many exfoliated vaginal epithelial cells caused by hyperplasia of normal pregnancy. This vaginal discharge is never pruritic or blood stained. Because of the progesterone effect, ferning usually does not occur in the dried cervical mucous smear, as it would in a smear of amniotic fluid. Instead, a beaded or cellular crystallizing pattern formed in the dried mucus is seen (Cunningham et al., 2001). The mucus fills the endocervical canal, resulting in the formation of the mucous plug (operculum) (Fig. 6). The operculum acts as a barrier against bacterial invasion during pregnancy

 

Fig. 6 A, Cervix in nonpregnant woman. B, Cervix during pregnancy.

 

During pregnancy, the pH of vaginal secretions ranges from approximately 3.5 to 6. The increased production of lactic acid in the vaginal epithelium, probably caused by increased estrogen levels, produces a more acid environment. However, the pregnant woman is more vulnerable to some vaginal infections, especially yeast infections (Bennett & Brown, 1999).

The increased vascularity of the vagina and other pelvic viscera results in a marked increase in sensitivity. The increased sensitivity may lead to a high degree of sexual interest and arousal, especially during the second trimester of pregnancy. The increased congestion plus the relaxed walls of the blood vessels and the heavy uterus may result in edema and varicosities of the vulva. The edema and varicosities usually resolve during the postpartum period.

External structures of the perineum are enlarged during pregnancy because of an increase in vasculature, hypertrophy of the perineal body, and deposition of fat (Fig. 7). The labia majora of the nullipara approximate and obscure the vaginal introitus; those of the parous woman separate and gape after childbirth and perineal or vaginal injury. Fig. 1 compares the perineum of the nullipara and the multipara in relation to the pregnant abdomen, vulva, and cervix.

 

 

Fig. 7 A, Pelvic floor in nonpregnant woman. B, Pelvic floor at end of pregnancy. Note marked hypertrophy and hyperplasia below dashed line joining tip of coccyx and inferior margin of symphysis. Note elongation of bladder and urethra as a result of compression. Fat deposits are increased.

 

Breasts

Fullness, heightened sensitivity, tingling, and heaviness of the breasts begins in the early weeks of gestation in response to increased levels of estrogen and progesterone. Breast sensitivity varies from mild tingling to sharp pain. Nipples and areolae become more pigmented; secondary pinkish areolae develop, extending beyond the primary areolae; and nipples become more erectile. Hypertrophy of the sebaceous (oil) glands embedded in the primary areolae, called Montgomery tubercles , may be seen around the nipples. These sebaceous glands may have a protective role in that they keep the nipples lubricated for breastfeeding.

The richer blood supply causes the vessels beneath the skin to dilate. Once barely noticeable, the blood vessels become visible, often appearing in an intertwining blue network beneath the surface of the skin. Venous congestion in the breasts is more obvious in primigravidas. Striae gravidarum may appear at the outer aspects of the breasts.

During the second and third trimesters, growth of the mammary glands accounts for the progressive breast enlargement. The high levels of luteal and placental hormones in pregnancy promote proliferation of the lactiferous ducts and lobule-alveolar tissue, so palpation of the breasts reveals a generalized, coarse nodularity. Glandular tissue displaces connective tissue, and as a result the tissue becomes softer and looser.

Although development of the mammary glands is functionally complete by midpregnancy, lactation is inhibited until a drop in estrogen level occurs after the birth. A thin, clear, viscous secretory material (precolostrum) can be found in the acini cells by the third month of gestation.

Colostrum, the creamy, white/yellowish to orange premilk fluid, may be expressed from the nipples as early as 16 weeks of gestation (Lawrence, 1999). See Chapter 20 for discussion of lactation.

 

GENERAL BODY SYSTEMS

Cardiovascular system

Maternal adjustments to pregnancy involve extensive changes in the cardiovascular system, both anatomic and physiologic. Cardiovascular adaptations protect the woman's normal physiologic functioning, meet the metabolic demands pregnancy imposes on her body, and provide for fetal developmental and growth needs.

Slight cardiac hypertrophy (enlargement) is probably secondary to the increased blood volume and cardiac output that occurs. The heart returns to its normal size after childbirth. As the diaphragm is displaced upward by the enlarging uterus, the heart is elevated upward and rotated forward to the left (Fig. 8). The apical impulse, a point of maximum intensity, is shifted upward and laterally approximately 1 to 1.5 cm. The degree of shift depends on the duration of pregnancy and the size and position of the uterus.

 

 

Fig. 8 Changes in position of heart, lungs, and thoracic cage in pregnancy. Dashed line, nonpregnant; solid line, change that occurs in pregnancy.

 

The changes in heart size and position and increases in blood volume and cardiac output contribute to auscultatory changes common in pregnancy. There is more audible splitting of Sx and S2, and S, may be readily heard after 20 weeks of gestation. In addition, systolic and diastolic murmurs may be heard over the pulmonic area. These are transient and disappear shortly after the woman gives birth (Cunningham et al., 2001).

Between 14 and 20 weeks of gestation, the pulse increases approximately 10 to 15 beats per minute (beats/ min), which then persists to term. Palpitations may occur. In twin gestations, the maternal heart rate increases significantly in the third trimester (Creasy & Resnik, 1999).

The cardiac rhythm may be disturbed. The pregnant woman may experience sinus arrhythmia, premature atrial contractions, and premature ventricular systole. In the healthy woman with no underlying heart disease, no therapy is needed; however, women with preexisting heart disease will need close medical and obstetric supervision during pregnancy.

Blood pressure. Arterial blood pressure (brachial artery) is affected by age, activity level, and presence of health problems. Additional factors must be considered during pregnancy. These factors include maternal anxiety, maternal position, and size and type of blood pressure apparatus.

Maternal anxiety can elevate readings. If an elevated reading is found, the woman is given time to rest, and the reading is repeated.

Maternal position affects readings. Brachial blood pressure is highest when the woman is sitting, lowest when she is lying in the lateral recumbent position, and intermediate when she is supine, except for some women who experience supine hypotensive syndrome (see following discussion). Therefore, at each prenatal visit, the reading should be obtained in the same arm and with the woman in the same position. The position and arm used should be recorded along with the reading.

The proper size cuff is absolutely necessary for accurate readings. The cuff should be 20% wider than the diameter of the arm around which it is wrapped, or approximately 12 to 14 cm for average-sized individuals and 18 to 20 cm for obese persons. Too small a cuff yields a false-high reading; too large a cuff yields a false-low reading. Caution should also be used when comparing auscultatory and oscillatory blood pressure readings because discrepancies can occur (Green & Froman, 1996).

In the first trimester, blood pressure usually remains the same as the prepregnancy level. During the second trimester, there is a decrease in both systolic and diastolic pressure of 5 to 10 mm Hg. This decrease is probably the result of peripheral vasodilation caused by hormonal changes that occur during pregnancy. During the third trimester, maternal blood pressure should return to the first-trimester levels.

Calculating the mean arterial pressure (MAP) (mean of the blood pressure in the arterial circulation) can increase the diagnostic value of the findings. Normal MAP readings in the nonpregnant woman are 86.4 ± 7.5 mm Hg. MAP readings for a pregnant woman are slightly higher (Creasy 6 Resnik, 1999). One way to calculate MAP is illustrated in Box 1

Box 1 Calculation of Mean Arterial Pressure (MAP)

 

Some degree of compression of the vena cava occurs in all women who lie flat on their backs during the second half of pregnancy . Some women experience a fall in their systolic blood pressure of more than 30 mm Hg. After 4 to 5 minutes a reflex bradycardia is noted, cardiac output is reduced by half, and the woman feels faint. This condition is termed supine hypotensive syndrome (Cunningham et al., 2001).

Compression of the iliac veins and inferior vena cava by the uterus causes increased venous pressure and reduced blood flow in the legs (except when the woman is in the lateral position). These alterations contribute to the dependent edema, varicose veins in the legs and vulva, and hemorrhoids that develop in the latter part of term pregnancy (Fig. 9).

 

 

Fig. 9 Hemorrhoids. (Courtesy Marjorie Pyle, RNC, Lifecircle, Costa Mesa, CA.)

 

Blood volume and composition. The degree of blood volume expansion varies considerably. Blood volume increases by approximately 1500 ml, or 40% to 45% above nonpregnancy levels (Cunningham et al., 2001). This increase consists of 1000 ml of plasma plus 450 ml of red blood cells (RBCs). The blood volume starts to increase at approximately the tenth to twelfth week, peaks at approximately the thirty-second to thirty-fourth week, then decreases slightly at the fortieth week. The increase in volume of a multiple gestation is greater than that for a pregnancy with a single fetus (Creasy & Resnik, 1999). Increased volume is a protective mechanism. It is essential for meeting the blood volume needs of the hypertrophied vascular system of the enlarged uterus, adequately hydrating fetal and maternal tissues when the woman assumes an erect or a supine position, and providing a fluid reserve to compensate for blood loss during birth and the puerperium. Peripheral vasodilation maintains a normal blood pressure despite the increased blood volume in pregnancy.

During pregnancy there is an accelerated production of RBCs (normal 4.2 to 5.4 million/mm3). The percentage of increase depends on the amount of iron available. The RBC mass increases by approximately 17% (Creasy & Resnik, 1999).

Because the plasma increase exceeds the increase in RBC production, there is a decrease in normal hemoglobin values (12 to 16 g/dl blood) and hematocrit values (37% to 47%). This state of hemodilution is referred to as physiologic anemia. The decrease is more noticeable during the second trimester, when rapid expansion of blood volume takes place faster than RBC production. If the hemoglobin value drops to 10 g/dl or less or if the hematocrit drops to 35% or less, the woman is considered anemic.

The total white cell count increases during the second trimester and peaks during the third trimester. This increase is primarily in the granulocytes; the lymphocyte count stays approximately the same throughout pregnancy. See Table 3 for laboratory values during pregnancy.

 

Table 3 Laboratory values for Pregnant and Nonpregnant Women
HEMATOLOGIC VALUES Complete Blood Count (CBC)
Hemoglobin (g/dl)	12-16*	>11*
Hematocrit, packed cell volume (%)	37-47	>33*
Red blood cell (RBC) volume (per ml)	1600	1500-1900
Plasma volume (per ml)	2400	3700
RBC count (million/mm3)	4.2-5.4	5-6.25
White blood cells (total per mm3)	5000-10,000	5000-15,000
Neutophils (%)	55-70	60-85
Lymphocytes (%)	20-40	15-40
Erythrocyte sedimentation rate (mm/hr)	20	Elevated second and third trimesters
Mean corpuscular hemoglobin concentration (MCHC) (g/dl packed RBCs)	32-36	No change hemoglobin concentration
Mean corpuscular hemoglobin (MCH) (pg)	27-31	No change per picogram (less than a nanogram)
Mean corpuscular volume (MCV) (yu.m3)	80-95	No change per cubic micrometer
Blood Coagulation and Fibrinolytic Activityt
Factor	65-140	Increase in pregnancy, return to normal in early puerperium; factor VIII increases during and immediately after birth
Factor	55-145
Factor	60-140
Factor	45-155
Factor	65-135	Decrease in pregnancy
Factor	50-150
Prothrombin time (PT) (sec)	11-12.5	Slight decrease in pregnancy
Partial thromboplastin time (PTT) (sec)	60-70	Slight decrease in pregnancy, and decreases further during second and third stages of labor (indicates clotting at placental site)
Bleeding time (min)	1-9 (Ivy)	No appreciable change
Coagulation time (min)	6-10 (Lee/White)	No appreciable change
Platelets (per mm3)	150,000-400,000	No significant change until 3-5 days after birth and then a rapid increase (may predispose woman to thrombosis) and gradual return to normal
Fibrinolytic activity		Decreases in pregnancy and then abrupt return to normal (protection against thromboembolism)
Fibrinogen (mg/dl)	200-400	Increased levels late in pregnancy
Mineral/Vitamin Concentrations
Vitamin B12, folic acid, ascorbic acid
Serum proteins Total (g/dl) Albumin (g/dl) Globulin, total (g/dl)	6.4-8.3 3.5-5.0 2.3-3.4	5.5-7.5 Slight increase 3-4
Blood glucose Fasting (mg/dl) 2-Hour postprandial (mg/dl)	70-105 <140	Decreases <140 after a 100-g carbohydrate meal is considerednormal
Acid-Base Values in Arterial Blood
Po2	80-100	104-108 (increased)
Pco2	35-45	27-32 (decreased)
Sodium bicarbonate (HCO3) (mEq/L)	21-28	18-31 (decreased)
Blood	7.35-7.45	7.40-7.45 (slightly increased —more alkaline)
HEPATIC VALUES
Bilirubin total (mg/dl)	Not more than 1 mg/dl	Unchanged
Serum cholesterol (mg/dl)	120-200	Increases from 16-32 weeks of pregnancy; remains at this level until after birth
Serum alkaline phosphatase (U/L)	30-120	Increases from week 12 of pregnancy to 6 weeks after birth
Serum albumin (g/dl)	3.5-5	Slight increase
RENAL VALUES
Bladder capacity (ml)	1300	1500
Renal plasma flow (RPF) (ml/min	490-700	Increase by 25%-30%
Glomerular filtration rate (GFR) (ml/min)	88-128	Increase by 30%-50%
Nonprotein nitrogen (NPN) (mg/dl)	25-40	Decreases
Blood urea nitrogen (BUN) (mg/dl)	10-20	Decreases
Serum creatinine (mg/dl)	0.5-1.1	Decreases
Serum uric acid (mg/dl)	2.7-7.3	Decreases
Urine glucose	Negative	Present in 20% of pregnant women
Intravenous pyelogram (IVP)	Normal	Slight to moderate hydroureter and hydronephrosis; right kidney larger than left kidney

 

Cardiac output. Cardiac output increases from 30% to 50% over the nonpregnant rate by the thirty-second week of pregnancy; it declines to approximately a 20% increase at 40 weeks of gestation. This elevated cardiac output is largely a result of increased stroke volume and heart rateand occurs in response to increased tissue demands for oxygen (Creasy & Resnik, 1999). Cardiac output in late pregnancy is appreciably higher when the woman is in the lateral recumbent position than when she is supine. In the supine position, the large, heavy uterus often impedes venous return to the heart and affects blood pressure. Cardiac output increases with any exertion, such as labor and birth. (Table 4 summarizes cardiovascular changes in pregnancy.)

 

TABLE 4 Cardiovascular Changes in Pregnancy
Heart rate	Increases 10-15 beats/min
Blood pressure	Remains at prepregnancy levels in first trimester Slight decrease in second trimester Returns to prepregnancy levels in third trimester
Blood volume	Increases by 1500 ml or 40%-45% above prepregnancy level
Red blood cell mass	Increases 17%
Hemoglobin	Decreases
Hematocrit	Decreases
White blood cell count	Increases in second and third trimester
Cardiac output	Increases 30%-50%

 

Circulation and coagulation times. The circulation time decreases slightly by week 32. It returns to near normal near term. There is a greater tendency for blood to coagulate (clot) during pregnancy because of increases in various clotting factors (factors VII, VIII, IX, X, and fibrinogen). This, combined with the fact that fibrinolytic activity (the splitting up or the dissolving of a clot) is depressed during pregnancy and the postpartum period, provides a protective function to decrease the chance of bleeding but also makes the woman more vulnerable to thrombosis, especially after cesarean birth.

 

Respiratory system

Structural and ventilatory adaptations occur during pregnancy to provide for maternal and fetal needs. Maternal oxygen requirements increase in response to the acceleration in the metabolic rate and the need to add to the tissue mass in the uterus and breasts. In addition, the fetus requires oxygen and a way to eliminate carbon dioxide.

Elevated levels of estrogen cause the ligaments of the rib cage to relax, permitting increased chest expansion (see Fig. 8). The transverse diameter of the thoracic cage increases by approximately 2 cm, and the circumference increases by 6 cm (Cunningham et al., 2001). The costal angle increases and the lower rib cage appears to flare out. The chest may not return to its prepregnant state after birth (Seidel et al., 1999).

The diaphragm is displaced by as much as 4 cm during pregnancy. As pregnancy advances, thoracic (costal) breathing replaces abdominal breathing, and it becomes less possible for the diaphragm to descend with inspiration. Thoracic breathing is primarily accomplished by the diaphragm rather than by the costal muscles (Creasy & Resnik, 1999).

The upper respiratory tract becomes more vascular in response to elevated levels of estrogen. As the capillaries become engorged, edema and hyperemia develop within the nose, pharynx, larynx, trachea, and bronchi. This congestion within the tissues of the respiratory tract gives rise to several conditions commonly seen during pregnancy. These conditions include nasal and sinus stuffiness, epistaxis (nosebleed), changes in the voice, and a marked inflammatory response that can develop into a mild upper respiratory infection.

Increased vascularity of the upper respiratory tract also can cause the tympanic membranes and eustachian tubes to swell, giving rise to symptoms of impaired hearing, earaches, or a sense of fullness in the ears.

Pulmonary function. Respiratory changes in pregnancy are related to the elevation of the diaphragm and chest wall changes (Creasy & Resnik, 1999). Changes in the respiratory center result in a lowered threshold for carbon dioxide. The actions of progesterone and estrogen are presumed responsible for the increased sensitivity of the respiratory center to carbon dioxide. In addition, pregnant women become more aware of the need to breathe; some may even complain of dyspnea at rest. (See Table 5 for respiratory changes in pregnancy.)

 

Table 5 Respiratory Changes in Pregnancy
Respiratory rate	Unchanged or slightly increased
Tidal volume	Increased 30%-40%
Vital capacity	Unchanged
Inspiratory	Increased
Expiratory	Decreased
Total	Unchanged to slightly decreased
Oxygen consumption	Increased 15%-20%

 

Although pulmonary function is not impaired by pregnancy, diseases of the respiratory tract may be more serious during this time (Cunningham et al., 2001). One important factor responsible for this may be the increased oxygen requirement.

Basal metabolism rate. The basal metabolism rate (BMR) varies considerably in women at the beginning of and during pregnancy, although it usually increases by 15% to 20% at term (Worthington-Roberts & Williams, 1997). The BMR returns to nonpregnant levels by 5 to 6 days postpartum. The elevation in BMR during pregnancy reflects increased oxygen demands of the uterineplacental-fetal unit and greater oxygen consumption because of increased maternal cardiac work (Chamberlain & Pipkin, 1998). Peripheral vasodilation and acceleration of sweat gland activity help dissipate the excess heat resulting from the increased BMR during pregnancy. Pregnant women may experience heat intolerance, which is annoying to some women. Lassitude and fatigability after only slight exertion are experienced by many women in early pregnancy. These feelings, along with a greater need for sleep, may persist and may be caused in part by the increased metabolic activity.

Acid-base balance. Around the tenth week of pregnancy, there is a decrease of approximately 5 mm Hg in the partial pressure of carbon dioxide (PCO2). Progesterone may be responsible for increasing the sensitivity of the respiratory center receptors so that tidal volume is increased and PCO2 falls, the base excess (HCO3, or bicarbonate) falls, and pH increases slightly. These alterations in acidbase balance indicate that pregnancy is a state of respiratory alkalosis compensated by mild metabolic acidosis (Chamberlain & Pipkin, 1998). These changes also facilitate the transport of CO2 from the fetus and O2 release from the mother to the fetus (see Table 3).

 

Renal system

The kidneys are responsible for maintaining electrolyte and acid-base balance, regulating extracellular fluid volume, excreting waste products, and conserving essential nutrients.

Anatomic changes. Changes in renal structure during pregnancy result from hormonal activity (estrogen and progesterone), pressure from an enlarging uterus, and an increase in blood volume. As early as the tenth week of pregnancy, the renal pelves and the ureters dilate. Dilation of the ureters is more pronounced above the pelvic brim, in part because they are compressed between the uterus and the pelvic brim. In most women the ureters below the pelvic brim are of normal size. The smooth muscle walls of the ureters undergo hyperplasia and hypertrophy and muscle tone relaxation. The ureters elongate, become tortuous, and form single or double curves. In the latter part of pregnancy, the renal pelvis and ureter are dilated more on the right side than on the left because the heavy uterus is displaced to the right by the sigmoid colon.

Because of these changes, a larger volume of urine is held in the pelves and ureters, and urine flow rate is slowed. The resulting urinary stasis or stagnation has the following consequences:

• There is a lag between the time urine is formed and when it reaches the bladder. Therefore clearance test results may reflect substances contained in glomerular filtrate several hours before.

• Stagnated urine is an excellent medium for the growth of microorganisms. In addition, the urine of pregnant women contains more nutrients, including glucose, thereby increasing the pH (making the urine more alkaline). This makes pregnant women more susceptible to urinary tract infection.

Bladder irritability, nocturia, and urinary frequency and urgency (without dysuria) are commonly reported in early pregnancy. Near term, bladder symptoms may return, especially after lightening occurs.

Urinary frequency results initially from increased bladder sensitivity and later from compression of the bladder (see Fig. 7). In the second trimester the bladder is pulled up out of the true pelvis into the abdomen. The urethra lengthens to 7.5 cm as the bladder is displaced upward. The pelvic congestion that occurs in pregnancy is reflected in hyperemia of the bladder and urethra. This increased vascularity causes the bladder mucosa to be traumatized and bleed easily. Bladder tone may decrease, which increases the bladder capacity to 1500 ml. At the same time the bladder is compressed by the enlarging uterus, resulting in the urge to void even if the bladder contains only a small amount of urine.

Functional changes. In normal pregnancy, renal function is altered considerably. Glomerular filtration rate (GFR) and renal plasma flow increase early in pregnancy (Cunningham et al., 2001). These changes are caused by pregnancy hormones, an increase in blood volume, the woman's posture, physical activity, and nutritional intake. The woman's kidneys must manage the increased metabolic and circulatory demands of the maternal body and also excretion of fetal waste products. Renal function is most efficient when the woman lies in the lateral recumbent position and least efficient when the woman assumes a supine position. A side-lying position increases renal perfusion, which increases urinary output and decreases edema. When the pregnant woman is lying supine, the heavy uterus compresses the vena cava and the aorta, and cardiac output decreases. As a result, blood flow to the brain and heart is continued at the expense of other organs, including the kidneys and uterus.

Fluid and electrolyte balance. Selective renal tubular reabsorption maintains sodium and water balance regardless of changes in dietary intake and losses through sweat, vomitus, or diarrhea. From 500 to 900 mEq of sodium is normally retained during pregnancy to meet fetal needs. To prevent excessive sodium depletion, the maternal kidneys undergo a significant adaptation by increasing tubular reabsorption. Because of the need for increased maternal intravascular and extracellular fluid volume, additional sodium is needed to expand fluid volume and to maintain an isotonic state. As efficient as the renal system is, it can be overstressed by excessive dietary sodium intake or restriction or by use of diuretics. Severe hypovolemia and reduced placental perfusion are two consequences of using diuretics during pregnancy.

The capacity of the kidneys to excrete water during the early weeks of pregnancy is more efficient than later in pregnancy. As a result, some women feel thirsty in early pregnancy because of the greater amount of water loss. The pooling of fluid in the legs in the latter part of pregnancy decreases renal blood flow and GFR. This pooling of blood in the lower legs is sometimes referred to as physiologic edema or dependent edema and requires no treatment. The normal diuretic response to the water load is triggered when the woman lies down, preferably on her side, and the pooled fluid reenters general circulation.

Normally, the kidney reabsorbs almost all of the glucose and other nutrients from the plasma filtrate. In pregnant women, however, tubular reabsorption of glucose is impaired so that glucosuria occurs at varying times and to varying degrees. Normal values range from 0 to 20 mg/dl, meaning that during any one day the urine is sometimes positive and sometimes negative. In nonpregnant women, blood glucose levels must be at 160 to 180 mg/dl before glucose is "spilled" into the urine (not reabsorbed). During pregnancy, glycosuria occurs when maternal glucose levels are lower than 160 mg/dl. Why glucose, as well as other nutrients such as amino acids, is wasted during pregnancy is not understood, nor has the exact mechanism been discovered. Although glycosuria may be found in normal pregnancies (2 + levels may be seen with increased anxiety states), the possibility of diabetes mellitus and gestational diabetes must be kept in mind.

Proteinuria usually does not occur in normal pregnancy except during labor or after birth (Cunningham et al., 2001). However, the increased amount of amino acids that must be filtered may exceed the capacity of the renal tubules to absorb it, so small amounts of protein are then lost in the urine. Values of trace to +1 protein (dipstick assessment) or less than 300 mg/24 hr are acceptable during pregnancy (Creasy & Resnik, 1999). The amount of protein excreted is not an indication of the severity of renal disease, nor does an increase in protein excretion in a pregnant woman with known renal disease necessarily indicate a progression in her disease. However, a pregnant woman with hypertension and proteinuria must be carefully evaluated because she may be at greater risk for an adverse pregnancy outcome (see Table 3).

 

Integumentary system

Alterations in hormonal balance and mechanical stretching are responsible for several changes in the integumentary system during pregnancy. Hyperpigmentation is stimulated by the anterior pituitary hormone melanotropin, which is increased during pregnancy. Darkening of the nipples, areolae, axillae, and vulva occurs at approximately the sixteenth week of gestation. Facial melasma, also called chloasma or "mask of pregnancy," is a blotchy, brownish hyperpigmentation of the skin over the cheeks, nose, and forehead, especially in dark-complexioned pregnant women. Chloasma appears in 50% to 70% of pregnant women, beginning after the sixteenth week and increasing gradually until term. The sun intensifies this pigmentation in susceptible women. Chloasma caused by normal pregnancy usually fades after birth.

The linea nigra (Fig. 10) is a pigmented line extending from the symphysis pubis to the top of the fundus in the midline; this line is known as the linea alba before hormoneinduced pigmentation. In primigravidas the extension of the linea nigra, beginning in the third month, keeps pace with the rising height of the fundus; in multigravidas the entire line often appears earlier than the third month. Not all pregnant women develop linea nigra.

 

 

Fig. 10 Linea nigra. (From Seidel, H. et al. [1999]. Mosby's guide to physical examination [4th ed.]. St. Louis: Mosby.)

 

Striae gravidarum, or stretch marks (seen over lower abdomen in Fig. 11), which appear in 50% to 90% of pregnant women during the second half of pregnancy, may be caused by action of adrenocorticosteroids. Striae reflect separation within the underlying connective (collagen) tissue of the skin. These slightly depressed streaks tend to occur over areas of maximum stretch (i.e., abdomen, thighs, and breasts). The stretching sometimes causes a sensation that resembles itching. The tendency to develop striae may be familial. After birth they usually fade, although they never disappear completely. Color of striae varies depending on the pregnant woman's skin color. The striae appear pinkish on a woman with light skin and are lighter than surrounding skin in dark-skinned women. In the multipara, in addition to the striae of the present pregnancy, glistening silvery lines (in light-skinned women) or purplish lines (in dark-skinned women) are commonly seen. These represent the scars of striae from previous pregnancies.

 

Fig. 11 Striae gravidarum, or "stretch marks." (Courtesy Michael S. Clement, MD, Mesa, AZ.)

 

Angiomas are commonly referred to as vascular spiders.They are tiny, star-shaped or branched, slightly raised and pulsating end-arterioles usually found on the neck, thorax, face, and arms. They occur as a result of elevated levels of circulating estrogen. The spiders are bluish in color and do not blanch with pressure. Vascular spiders appear during the second to the fifth month of pregnancy in 65% of Caucasian women and 10% of African-American women. The spiders usually disappear after birth.

Pinkish red, diffuse mottling or well-defined blotches are seen over the palmar surfaces of the hands in approximately 60% of Caucasian women and 35% of African-American women during pregnancy (Cunningham et al., 2001). These color changes, called palmar erythema, are related primarily to increased estrogen levels.

Pruritus is a relatively common dermatologic symptom in pregnancy, with cholestasis of pregnancy being the most common cause of pruritic rash. The goal of management is to relieve the itching. Topical steroids are the usual treatment, although systemic steroids may be needed. The problem usually resolves in the postpartum period (Gordon & Landon, 1996).

Gum hypertrophy may occur. An epulis (gingival granuloma gravidarum) is a red, raised nodule on the gums that bleeds easily. This lesion may develop around the third month and usually continues to enlarge as pregnancy progresses. It is usually managed by avoiding trauma to the gums (e.g., using a soft toothbrush). An epulis usually regresses spontaneously after birth.

Nail growth may be accelerated. Some women may notice thinning and softening of the nails. Oily skin and acne vulgaris may occur during pregnancy. For some women the skin clears and looks radiant. Hirsutism, the excessive growth of hair or growth of hair in unusual places, is commonly reported. An increase in fine hair growth may occur but tends to disappear after pregnancy. However, growth of coarse or bristly hair does not usually disappear after pregnancy.

Increased blood supply to the skin leads to increased perspiration. Women feel hotter during pregnancy, possibly related to a progesterone-induced increase in body temperature and the increased BMR.

 

Musculoskeletal system

The gradually changing body and increasing weight of the pregnant woman cause noticeable alterations in her posture (Fig. 12) and the way she walks. The great abdominal distention that gives the pelvis a forward tilt, decreased abdominal muscle tone, and increased weight bearing require a realignment of the spinal curvature late in pregnancy. The woman's center of gravity shifts forward. An increase in the normal lumbosacral curve (lordosis) develops, and a compensatory curvature in the cervicodorsal region (exaggerated anterior flexion of the head) develops to help her maintain her balance. Aching, numbness, and weakness of the upper extremities may result. Large breasts and a stoop-shouldered stance will further accentuate the lumbar and dorsal curves. Walking is more difficult, and the waddling gait of the pregnant woman, called "the proud walk of pregnancy" by Shakespeare, is well known. The ligamentous and muscular structures of the middle and lower spine may be severely stressed. These and related changes often cause musculoskeletal discomfort, especially in older women or those with a back disorder or a faulty sense of balance.

 

 

Fig. 12 Postural changes during pregnancy. A, Nonpregnant. B, Incorrect posture during pregnancy. C, Correct posture during pregnancy.

 

Slight relaxation and increased mobility of the pelvic joints are normal during pregnancy. They are secondary to the exaggerated elasticity and softening of connective and collagen tissue caused by increased circulating steroid sex hormones, especially estrogen. Relaxin, an ovarian hormone, assists in this relaxation and softening. These adaptations permit enlargement of pelvic dimensions to facilitate labor and birth. The degree of relaxation varies, but considerable separation of the symphysis pubis and the instability of the sacroiliac joints may cause pain and difficulty in walking. Obesity and multifetal pregnancy tend to increase the pelvic instability. Peripheral joint laxity also increases as pregnancy progresses, but the cause is not known (Schauberger et al., 1996).

The muscles of the abdominal wall stretch and ultimately lose some tone. During the third trimester the rectus abdominis muscles may separate (Fig. 13), allowing abdominal contents to protrude at the midline. The umbilicus flattens or protrudes. After birth, the muscles gradually regain tone. However, separation of the muscles (diastasis recti abdominis) may persist.

 

Fig. 13 Possible change in rectus abdominis muscles during pregnancy. A, Normal position in nonpregnant woman. B, Diastasis recti abdominis in pregnant woman.

 

Neurologic system

Little is known regarding specific alterations in function of the neurologic system during pregnancy, aside from hypothalamic-pituitary neurohormonal changes. Specific physiologic alterations resulting from pregnancy may cause the following neurologic or neuromuscular symptoms:

• Compression of pelvic nerves or vascular stasis caused by enlargement of the uterus may result in sensory changes in the legs.

• Dorsolumbar lordosis may cause pain because of traction on nerves or compression of nerve roots.

• Edema involving the peripheral nerves may result in carpal tunnel syndrome during the last trimester. The syndrome is characterized by paresthesia (abnormal sensation such as burning or tingling) and pain in the hand, radiating to the elbow. The sensations are caused by edema that compresses the median nerve beneath the carpal ligament of the wrist. The dominant hand is usually affected most, although as many as 80% of women experience symptoms in both hands. Symptoms usually regress after pregnancy. In some cases, surgical treatment may be necessary (Cunningham et al., 2001).

• Acroesthesia (numbness and tingling of the hands) is caused by the stoop-shouldered stance (see Fig. 12, B) assumed by some women during pregnancy. The condition is associated with traction on segments of the brachial plexus.

• Tension headache is common when anxiety or uncertainty complicates pregnancy. However, vision problems, sinusitis, or migraine may also be responsible for headaches.

• Light-headedness, faintness, and even syncope (fainting) are common during early pregnancy. Vasomotor instability, postural hypotension, or hypoglycemia may be responsible.

• Hypocalcemia may cause neuromuscular problems such as muscle cramps or tetany.

 

Gastrointestinal system

Appetite. During pregnancy, the pregnant woman's appetite and food intake fluctuate. Early in pregnancy, some women experience "morning sickness" in response to increasing levels of hCG and altered carbohydrate metabolism (see Research box). Morning sickness refers to nausea with or without vomiting. It appears at approximately 4 to 6 weeks of gestation and usually subsides by the end of the third month (first trimester) of pregnancy. Severity varies from mild distaste for certain foods to more severe vomiting. The condition may be triggered by the sight or odor of various foods. Fatigue may also be responsible for severe nausea, but further research is needed to determine the role of this factor (O'Brien & Zhou, 1995). By the end of the second trimester, the appetite increases in response to increasing metabolic needs. Rarely does morning sickness have harmful effects on the embryo/fetus or the woman. Whenever the vomiting is severe or persists beyond the first trimester, or when it is accompanied by fever, pain, or weight loss, further evaluation is necessary and medical intervention is likely.

Women may also experience changes in their sense of taste, leading to cravings and changes in dietary intake. Some women have nonfood cravings (pica) such as ice, clay, and laundry starch (Cunningham et al., 2001).

 

RESEARCH ACUPRESSURE INTERVENTION FOR NAUSEA AND VOMITING OF PREGNANCY Up to 70% of all pregnant women experience nausea and vomiting of pregnancy (NVP), typically between weeks 5 through 12 of gestation.This may lead to nutritional deficits, dehydration, and electrolyte imbalances. Employment and family functioning may be affected. Pharmacologic treatment for NVP may cause teratogenic effects to the fetus. Nonpharmacologic treatments, including vitamin B6 (pyridoxine); acupressure; certain eating and drinking patterns; and vitamin, herbal, and homeopathic remedies, are not well researched. This clinical study investigated the use of acupressure as a treatment of NVR A total of 110 first-trimester pregnant women with NVP were randomly assigned to wearing Sea-Bands or placebo wrist bands. Sea-Bands are an acupressure device consisting of an elastic band worn at the wrist that holds a button against a point 3 fingerbreadths below the wrist crease and between the two flexor tendons on the medial forearm. The placebos had no button. Days 1 through 4, the women wore their Sea-Band or placebo, then removed them for days 5 through 7, keeping seven daily logs of nausea and vomiting. Results showed that the Sea-Band group had significantly less nausea and vomiting than the placebo group while wearing the device.The Sea-Band group also had a significant rise in nausea and vomiting after the device was discontinued. In addition, women in the Sea-Band group who used vitamin B6 during the treatment had significantly more relief from nausea and vomiting than did nontakers, but this effect disappeared when the device was removed. IMPLICATION FOR PRACTICE Alternative and complementary treatments for women's health, including pregnancy, are numerous. Nurses need to be informed about the most current treatments for discomforts of pregnancy that are effective and at the same time safe, noninvasive, and inexpensive. This study suggests that acupressure can be recommended for relief of NVR   Source: Steel, N. et al. (2001). Effect of acupressure by Sea-Bands on nausea and vomiting of pregnancy. J Obstet Gyncol Neonatal Nurs, 30(1), 61-70.

 

 

Mouth. The gums become hyperemic, spongy, and swollen during pregnancy. They tend to bleed easily because the rising levels of estrogen cause selective increased vascularity and connective tissue proliferation (a nonspecific gingivitis). Epulis (discussed in the section on the integumentary system) may develop at the gumline. Some pregnant women complain of ptyalism (excessive salivation), which may be caused by the decrease in unconscious swallowing by the woman when nauseated or from stimulation of salivary glands by eating starch (Cunningham et al., 2001).

Esophagus, stomach, and intestines. Herniation of the upper portion of the stomach (hiatal hernia) occurs after the seventh or eighth month of pregnancy in approximately 15% to 20% of pregnant women. This condition results from upward displacement of the stomach, which causes the hiatus of the diaphragm to widen. It occurs more often in multiparas and older or obese women.

Increased estrogen production causes decreased secretion of hydrochloric acid. Therefore peptic ulcer formation or flare-up of existing peptic ulcers is uncommon during pregnancy.

Increased progesterone production causes decreased tone and motility of smooth muscles, resulting in esophageal regurgitation, slower emptying time of the stomach, and reverse peristalsis. As a result, the woman may experience "acid indigestion" or heartburn (pyrosis).

Iron is absorbed more readily in the small intestine in response to increased needs during pregnancy. Even when the woman is deficient in iron, it will continue to be absorbed in sufficient amounts for the fetus to have a normal hemoglobin level.

Increased progesterone (causing loss of muscle tone and decreased peristalsis) results in an increase in water absorption from the colon and may cause constipation. Constipation can also result from hypoperistalsis (sluggishness of the bowel), food choices, lack of fluids, iron supplementation, decreased activity level, abdominal distention by the pregnant uterus, and displacement and compression of the intestines. If the pregnant woman has hemorrhoids (see Fig. 9) and is constipated, the hemorrhoids may become everted or may bleed during straining at stool. A mild ileus (sluggishness and lack of movement resulting in obstruction) that follows birth, as well as postbirth fluid loss and perineal discomfort, contributes to continuing constipation.

Gallbladder and liver. The gallbladder is often distended because of its decreased muscle tone during pregnancy. Increased emptying time and thickening of bile caused by prolonged retention are typical changes. These features, together with slight hypercholesterolemia from increased progesterone levels, may account for the development of gallstones during pregnancy.

Hepatic function is difficult to appraise during pregnancy. However, only minor changes in liver function develop. Occasionally, intrahepatic cholestasis (retention and accumulation of bile in the liver, caused by factors within the liver) occurs late in pregnancy in response to placental steroids and may result in pruritus gravidarum (severe itching) with or without jaundice. These distressing symptoms subside soon after birth.

Abdominal discomfort. Intraabdominal alterations that can cause discomfort include pelvic heaviness or pressure, round ligament tension, flatulence, distention and bowel cramping, and uterine contractions. In addition to displacement of intestines, pressure from the expanding uterus causes an increase in venous pressure in the pelvic organs. Although most abdominal discomfort is a consequence of normal maternal alterations, the health care provider must be constantly alert to the possibility of disorders such as bowel obstruction or an inflammatory process.

Appendicitis may be difficult to diagnose in pregnancy because the appendix is displaced upward and laterally, high and to the right, away from McBurney's point (Fig. 14).

 

Fig. 14 Change in position of appendix in pregnancy. Note McBurney's point.

 

Endocrine system

Profound endocrine changes are essential for pregnancy maintenance, normal fetal growth, and postpartum recovery.

Pituitary and placental hormones. During pregnancy, the elevated levels of estrogen and progesterone (produced first by the corpus luteum in the ovary until approximately 14 weeks of gestation and then by the placenta) suppress secretion of follicle-stimulating hormone and luteinizing hormone by the anterior pituitary. The maturation of a follicle and ovulation do not occur. Although the majority of women experience amenorrhea (absence of menses), at least 20% have some slight, painless spotting during early gestation. Implantation bleeding and bleeding following intercourse related to cervical friability can occur. Most of the women experiencing slight gestational bleeding continue to full term and have normal infants. However, all instances of bleeding should be reported and evaluated.

After implantation, the fertilized ovum and the chorionic villi produce hCG, which maintains the corpus luteum's production of estrogen and progesterone until the placenta takes over their production (Creasy & Resnik, 1999).

Progesterone is essential for maintaining pregnancy by relaxing smooth muscles, resulting in decreased uterine contractility and prevention of miscarriage. Progesterone and estrogen cause fat to deposit in subcutaneous tissues over the maternal abdomen, back, and upper thighs. This fat serves as an energy reserve for both pregnancy and lactation. Estrogen also promotes the enlargement of the genitals, uterus, and breasts and increases vascularity, causing vasodilation. Estrogen causes relaxation of pelvic ligaments and joints. It also alters metabolism of nutrients by interfering with folic acid metabolism, increasing the level of total body proteins, and promoting retention of sodium and water by kidney tubules. Estrogen may decrease secretion of hydrochloric acid and pepsin, which may be responsible for digestive upsets such as nausea.

Serum prolactin produced by the anterior pituitary begins to rise early in the first trimester and increases progressively to term. It is responsible for initial lactation; however, the high levels of estrogen and progesterone inhibit lactation by blocking the binding of prolactin to breast tissue until after birth (Guyton & Hall, 1997).

Oxytocin is produced by the posterior pituitary in increasing amounts as the fetus matures. This hormone can stimulate uterine contractions during pregnancy, but high levels of progesterone prevent contractions until near term. Oxytocin also stimulates the let-down or milk-ejection reflex after birth in response to the infant sucking at the mother's breast.

Human chorionic somatomammotropin (hCS), previously called human placental lactogen, is produced by the placenta, acts as a growth hormone, and contributes to breast development. It decreases the maternal metabolism of glucose and increases the amount of fatty acids for metabolic needs (Alsat et al., 1997; Guyton & Hall, 1997).

Thyroid gland. During pregnancy there is an increase in gland activity and hormone production. The increased activity is reflected in a moderate enlargement of the thyroid gland caused by hyperplasia of the glandular tissue and increased vascularity (Cunningham et al., 2001). Thyroxine-binding globulin increases as a result of increased estrogen levels. This increase begins at approximately 20 weeks of gestation. The level of total (free and bound) thyroxine (T4) increases between 6 and 9 weeks of gestation and plateaus at 18 weeks of gestation. Free T4 and free triiodothyronine (T3) return to nonpregnant levels after the first trimester. Despite these changes in hormone production, the pregnant woman usually does not develop hyperthyroidism (Cunningham et al., 2001).

Parathyroid gland. Parathyroid hormone controls calcium and magnesium metabolism. Pregnancy induces a slight hyperparathyroidism, a reflection of increased fetal requirements for calcium and vitamin D. The peak level of parathyroid hormone occurs between 15 and 35 weeks of gestation when the needs for growth of the fetal skeleton are greatest. Levels return to normal after birth.

Pancreas. The fetus requires significant amounts of glucose for its growth and development. To meet its need for fuel, the fetus not only depletes the store of maternal glucose but also decreases the mother's ability to synthesize glucose by siphoning off her amino acids. Maternal blood glucose levels fall. Maternal insulin does not cross the placenta to the fetus. As a result, in early pregnancy, the pancreas decreases its production of insulin.

As pregnancy continues, the placenta grows and produces progressively larger amounts of hormones (i.e., hCS, estrogen, and progesterone). Cortisol production by the adrenals also increases. Estrogen, progesterone, hCS, and cortisol collectively decrease the mother's ability to use insulin. Cortisol stimulates increased production of insulin but also increases the mother's peripheral resistance to insulin (i.e., the tissues cannot use the insulin). Decreasing the mother's ability to use her own insulin is a protective mechanism that ensures an ample supply of glucose for the needs of the fetoplacental unit. The result is an added demand for insulin by the mother that continues to increase at a steady rate until term. The normal beta cells of the islets of Langerhans in the pancreas can meet this demand for insulin.

Adrenal glands. The adrenal glands change little during pregnancy. Secretion of aldosterone is increased, resulting in reabsorption of excess sodium from the renal tubules. Cortisol levels are also increased (Chamberlain & Pipkin, 1998).

 MATERNAL AND FETAL NUTRITION

Nutrition is one of the many factors that influence the outcome of pregnancy (Fig. 1). However, maternal nutritional status is an especially significant factor, both because it is potentially alterable and because good nutrition before and during pregnancy is an important preventive measure for a variety of problems. These problems include birth of low-birth-weight (LBW) and preterm infants. It is essential that the importance of good nutrition be emphasized to all women of childbearing potential. Nutrition assessment, intervention, and evaluation must be an integral part of nursing care for all pregnant women.

 

Fig, 1 Web of influences that can affect outcome of pregnancy. (From Wardlaw, G., & Insel, P. [1993]. Perspectives in nutrition. St. Louis: Mosby.)

NUTRIENT NEEDS BEFORE CONCEPTION

A healthful diet before conception is the best way to ensure that adequate nutrients are available for the developing fetus. Folic acid (folate) intake is of particular concern before conception and during early gestation, because neural tube defects (i.e., failure of the neural tube to close) are more common in infants of women with poor folic acid intake. It is estimated that the incidence of neural tube defects could be halved if all women had an adequate folic acid intake during this period (Butterworth & Bendich, 1996). All women capable of becoming pregnant are advised to consume 400 p,g of folic acid daily in fortified foods (e.g., ready-to-eat cereals and enriched grain products) or supplements, in addition to a diet rich in folic acid-containing foods: green leafy vegetables, whole grains, and meats.

Both maternal and fetal risks in pregnancy are increased when the mother is significantly underweight or overweight when pregnancy begins. Ideally, all women would achieve their desirable body weights before conception.

NUTRIENT NEEDS DURING PREGNANCY

Nutrient needs are determined, at least in part, by the stage of gestation in that the amount of fetal growth varies during the different stages of pregnancy. During the first trimester the synthesis of fetal tissues places relatively few demands on maternal nutrition. Therefore, during the first trimester, when the embryo/fetus is very small, the needs are only slightly increased over those before pregnancy. In contrast, the last trimester- is a period of noticeable fetal growth when most of the deposition of fetal stores of energy sources and minerals occurs. Basal metabolic rates, when expressed as kilocalories (kcal) per minute, are approximately 20% higher in pregnant women than in nonpregnant women. This increase includes the energy cost for tissue synthesis.

Dietary reference intakes (DRIs) are a new approach that the Food and Nutrition Board of the National Academy of Sciences has adopted to provide new nutritional recommendations for the people of the United States; Health Canada is also involved in this effort (Yates, Schlicker, & Suitor, 1998). The DRIs consist of recommended dietary allowances (RDAs) and adequate intakes (AIs), as well as guidelines for avoiding excessive nutrient intakes. RDAs are recommendations for daily nutritional intakes that meet the needs of almost all of the healthy members of the population. AIs are similar to the RDAs except that they are used when there are not enough data available to be certain that they meet the needs of the healthy population. The RDAs and the AIs include a wide variety of nutrients and food components, and they are divided into age, sex, and life-stage categories (e.g., infancy, pregnancy, lactation). They can be used as goals in planning the diets of individuals (Table 1).

TABLE 10-1 Nutritional RBcommendations During Pregnancy and Lactation
NUTRIENT (UNIT)	RECOMMENDATION FOR NONPREGNANT FEMALE*	RECOMMENDATION FOR PREGNANCY*	RECOMMENDATION FOR LACTATION*	ROLE IN RELATION TO PREGNANCY AND LACTATION	FOOD/FOOD SOURCES
Energy	Variable	First trimester, same as nonpregnant; second and third trimesters, nonpregnant + 300	Nonpregnant+ 500	Growth of fetal and maternal issues; milk production	Carbohydrate, fat, protein
Protein	50	60	65	Synthesis of the products of conception; growth of maternal tissue and expansion of blood volume; secretion of milk protein during lactation	Meats, eggs, cheese, yogurt, legumes (dry beans and peas, peanuts), nuts, grains
MINERALS
Calcium (mg)	1300/1000	1300/1000	1300/1000	Fetal and infant skeleton and tooth formation; maintenance of maternal bone and tooth mineralization	Milk, cheese, yogurt, sardines or other fish eaten with bones left in, deep green leafy vegetables except spinach or Swiss chard, tofu, baked beans
Phosphorus (mg)	1250/700	1250/700	1250/700	Fetal and infant skeleton and ooth formation	Milk, cheese, yogurt, meats, whole grains, nuts, legumes
Iron (mg)	15	30	15	Maternal hemoglobin formation, fetal liver iron storage	Liver, meats, whole or enriched breads and cereals, deep green leafy vegetables, legumes, dried fruits
Zinc (mg)	12	15	19	Component of numerous enzyme systems; possibly important in preventing congenital malformations	Liver, shellfish, meats, whole grains, milk
Iodine (|xg)	150	175	200	Increased maternal metabolic rate	Iodized salt, seafood, milk and milk products, commercial yeast breads, rolls, donuts
Magnesium (mg)	360/320	400/360	360/320	Involved in energy and protein metabolism, tissue growth, muscle action	Nuts, legumes, cocoa, meats, whole grains
FAT-SOLUBLE VITAMINS
A (RE)	800	800	1300	Essential for cell development, tooth bud formation, bone growth	Deep green leafy vegetables, dark yellow vegetables and fruits, chili peppers, liver, fortified margarine and butter
D (gμ)	5	5	5	Involved in absorption of calcium and phosphorus, improves mineralization	Fortified milk and margarine, egg yolk, butter, liver, seafood
E(mg)	8	10	12	Antioxidant (protects cell membranes from damage), especially important for preventing breakdown of RBCs	Vegetable oils, green leafy vegetables, whole grains, liver, nuts and seeds, cheese, fish
WATER-SOLUBLE VITAMINS
C (mg)	60	70	95	Tissue formation and integrity, formation of connective tissue, enhancement of iron absorption	Citrus fruits, strawberries, melons, broccoli, tomatoes, peppers, raw deep green leafy vegetables
Folic acid (gμ)	400	600	500	Prevention of neural tube defects, support increased maternal RBC formation	Fortified ready-to-eat cereals and other grains, green leafy vegetables, oranges, broccoli, asparagus, artichokes, liver
Thiamine (mg)	1.0/1.1	1.4	1.5	Involved in energy metabolism	Pork, beef, liver, whole or enriched grains, legumes
Riboflavin (mg)	1.0/1.1	1.4	1.6	Involved in energy and protein metabolism	Meat, liver, deep green vegetables, whole grains
Niacin (mg)	14	18	17	Involved in energy metabolism	Meat, fish, poultry, liver, whole or enriched grains, peanuts
Pyridoxine (B6) (mg)	1.2/1.3	1.9	2.0	Involved in protein metabolism	Meat, liver, deep green vegetables, whole grains
B12 (|xg)	2.4	2.6	2.8	Production of nucleic acids and proteins, especially important in formation of RBC and neural functioning	Milk and milk products, egg, meat, liver, fortified soy milk

 

Recommendations are the new dietary reference intakes (RDAor Al, see text) where available (Food and Nutrition Board, National Academy of Sciences, Institute of Medicine. [1998]. Recommended levels for individual intake, B vitamins, and choline. Washington, DC: National Academy Press; Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine. [1997]. Dietary reference intakes: Calcium, phosphorus, magnesium, vitamin D, and fluoride. Washington, DC: National Academy Press). Where DRI are not yet available, the values are taken from Food and Nutrition Board (1989).

RBC, Red blood cells.

*When two values appear, separated by a diagonal slash, the first is for females <19 years and the second is for those 19 to 50 years old.

ENERGY NEEDS

Energy (kilocalories; abbreviated kcal) needs are met by carbohydrate, fat, and protein in the diet. No specific recommendations exist for the amount of carbohydrate and fat in the diet of the pregnant woman. However, intake of these nutrients should be adequate to support the recommended weight gain. Although protein can be used to supply energy, its primary role is to provide amino acids for the synthesis of new tissues (see discussion on protein later in this chapter). The RDA during the second and third trimesters of pregnancy is 300 kcal greater than prepregnancy needs; very underweight or active women may require more than 300 additional kcal to sustain the desired rate of weight gain.

 

Weight gain

The optimal weight gain during pregnancy is not known precisely. It is known, however, that the amount of weight gained by the mother during pregnancy has an important bearing on the course and outcome of pregnancy.

Adequate weight gain reduces the risk of delivering a small for gestational age (SGA) or preterm infant.

The desirable weight gain during pregnancy varies among individual women. Maternal and fetal risks in pregnancy are increased when the mother is either significantly underweight or overweight before pregnancy and when weight gain during pregnancy is either too low or too high. Women with inadequate weight gain have an increased risk of delivering an infant with intrauterine growth restriction (IUGR). Greater-than-expected weight gain during pregnancy may occur for many reasons, including multiple gestation, edema, pregnancy-induced hypertension, and overeating. When obesity is present (either preexisting or developed during pregnancy), there is an increased likelihood of macrosomia and fetopelvic disproportion, operative birth, birth trauma, and infant death. Obese women are more likely to have hypertension and diabetes, and their risk of giving birth to a child with a major congenital defect is double that of normal-weight women (Prentice & Goldberg, 1996). The cost of pregnancy in an obese woman has been estimated to be triple that of a normal-weight woman (Prentice & Goldberg, 1996).

The primary factor to consider in making a weight gain recommendation is the appropriateness of the prepregnancy weight for the woman's height. A commonly used method of evaluating the appropriateness of weight for height is the body mass index (BMI), which is calculated by the following formula:

BMI = Weight/Height2

where the weight is in kilograms and height is in meters. Thus for a woman who weighed 51 kg before pregnancy and is 1.57 m tall:

BMI = 51/(1.57)2, or 20.7

BMI can be classified into the following categories: less than 19.8, underweight or low; 19.8 to 26.0, normal; 26.0 to 29.0, overweight or high; and greater than 29.0, obese.

For women with single fetuses, current recommendations are that women with a normal BMI should gain 11.5 to 16 kg during pregnancy, underweight women should gain 12.5 to 18 kg, overweight women should gain 7 to 11.5 kg, and obese women should gain at least 7 kg. Adolescents are encouraged to strive for weight gains at the upper end of the recommended range for their BMI because it appears that the fetus and the still-growing mother compete for nutrients. The risk of mechanical complications at birth is reduced if the weight gain of short adult women (i.e., less than 157 cm) is near the lower end of their recommended range. In twin gestations, gains of approximately 16 to 20 kg appear to be associated with the best outcomes (Ellings, Newman, & Bower, 1998).

 

PATTERN OF WEIGHT GAIN

Weight gain should take place throughout pregnancy. The risk of delivering an SGA infant is greater when the weight gain early in pregnancy has been poor. The likelihood of preterm birth is greater when the gains during the last half of pregnancy have been inadequate. These risks exist even when the total gain for the pregnancy is in the recommended range.

The optimal rate of weight gain depends on the stage of pregnancy. During the first and second trimesters, growth takes place primarily in maternal tissue; during the third trimester, growth occurs primarily in fetal tissues. During the first trimester there is an average total weight gain of only 1 to 2.5 kg. Thereafter the recommended weight gain increases to approximately 0.4 kg per week for a woman of normal weight (Fig. 2). The recommended weekly weight gain for overweight women during the second and third trimesters is 0.3 kg, and for underweight women it is 0.5 kg. The recommended caloric intake corresponds to this pattern of gain. For the first trimester there is no increment; during the second and third trimesters an additional 300 kcal/day over the prepregnant intake is recommended. The amount of food providing 300 kcal is not great. It can be provided by one additional serving from each of the following groups: milk, yogurt, or cheese (all skim milk products); fruits; vegetables; and bread, cereal, rice, or pasta.

 

Fig. 2 Prenatal weight gain chart for plotting weight gain of normal-weight women. Young adolescents, African-American women, and smokers should aim for the upper end of the recommended range; short women (less than 157 cm) should strive for gains at the lower end of the range.

 

The reasons for an inadequate weight gain (less than 1 kg per month for normal-weight women or less than 0.5 kg per month for obese women during the last two trimesters) or excessive weight gain (more than 3 kg per month) should be evaluated thoroughly. Possible reasons for deviations from the expected rate of weight gain include measurement or recording errors, differences in weight of clothing or time of day, and accumulation of fluids, as well as inadequate or excessive dietary intake. An exceptionally high gain is likely to be caused by an accumulation of fluids, and a gain of more than 3 kg in a month, especially after the twentieth week of gestation, often heralds the development of pregnancy-induced hypertension.

 

HAZARDS OF RESTRICTING ADEQUATE WEIGHT GAIN

An obsession with thinness and dieting permeates the North American culture. Slender, figure-conscious women may find it difficult to make the transition from guarding against weight gain before pregnancy to valuing weight gain during pregnancy. In counseling these women, the nurse can emphasize the positive effects of good nutrition, as well as the adverse effects of maternal malnutrition (manifested by poor weight gain) on infant growth and development. This counseling includes information on the components of weight gain during pregnancy (Fig. 3) and the amount of this weight that will be lost at birth. Early in a woman's pregnancy, explaining ways to lose weight in the postpartum period helps relieve her concerns. Because lactation can help to reduce maternal energy stores gradually, this provides an opportunity to promote breastfeeding.

 

Fig. 3 Components of maternal weight gain at 40 weeks of gestation. (Modified from Worthington-Roberts, B., & Williams, S. [1997]. Nutrition in pregnancy and lactation [6th ed.]. Dubuque, IA: Brown & Benchmark.)

 

Pregnancy is not a time to diet. Even overweight or obese pregnant women need to gain at least enough weight to equal the weight of the products of conception (i.e., fetus, placenta, and amniotic fluid). If they limit their caloric intake to prevent weight gain, they may also excessively limit their intake of important nutrients. Moreover, dietary restriction results in catabolism of fat stores, which in turn augments the production of ketones. The longterm effects of mild ketonemia during pregnancy are not known, but ketonuria has been found to be correlated with the occurrence of preterm labor. It should be stressed to obese women, and to all pregnant women, that the quality of the weight gain is important, with emphasis on the consumption of nutrient-dense foods and the avoidance of empty-calorie foods.

Weight gain is important, but pregnancy is not an excuse for uncontrolled dietary indulgence. Excessive weight gained during pregnancy may be difficult to lose after pregnancy, thus contributing to chronic overweight or obesity, an etiologic factor in a host of chronic diseases, including hypertension, diabetes mellitus, and arteriosclerotic heart disease. The woman who gains 18 kg or more during pregnancy is especially at risk.

 

Protein

Protein, with its essential constituent nitrogen, is the nutritional element basic to growth. Adequate protein is essential to meet increasing demands in pregnancy. These demands arise from the rapid growth of the fetus; the enlargement of the uterus and its supporting structures, mammary glands, and placenta; an increase in maternal circulating blood volume and the subsequent demand for increased amounts of plasma protein to maintain colloidal osmotic pressure; and the formation of amniotic fluid.

Milk, meat, eggs, and cheese are complete protein foods with a high biologic value. Legumes (dried beans and peas), whole grains, and nuts are also valuable sources of protein. In addition, these protein-rich foods are a source of other nutrients such as calcium, iron, and B vitamins; plant sources of protein often provide needed dietary fiber. The recommended daily food plan (Table 2) is a guide to the amounts of these foods that would supply the quantities of protein needed. The recommendations provide for only a modest increase in protein intake over the prepregnant levels in adult women. Protein intake in many people in the United States is relatively high, so many women may not need to increase their protein intake at all during pregnancy. Three servings of milk, yogurt, or cheese (four for adolescents) and 5 to 6 ounces (140 to 168 g) (two servings) of meat, poultry, or fish supply the recommended protein for the pregnant woman. Additional protein is provided by vegetables and breads, cereals, rice, and pasta. Pregnant adolescents, women from impoverished backgrounds, and women adhering to unusual diets such as a macrobiotic (highly restricted vegetarian) diet are those whose protein intake is most likely to be inadequate. The use of high-protein supplements is not recommended because they have been associated with an increased incidence of preterm births.

 

Table 2 Daily Food Guide for Pregnancy and Lactation

 

Fluids

Water is the main substance of cells, blood, lymph, amniotic fluid, and other vital body fluids and is essential during the exchange of nutrients and waste products across cell membranes. It also aids in maintaining body temperature. A good fluid intake promotes good bowel function, which is sometimes a problem during pregnancy. Dehydration may increase the risk of cramping/contractions and preterm labor. The recommended daily intake is 6 to 8 glasses (1500 to 2000 ml) of fluid. Water, milk, and juices are good sources of fluids.

Women who consume more than 300 mg of caffeine daily (equivalent to 500 to 750 ml of coffee) are at increased risk of miscarriage and of delivering infants with IUGR. Caffeine's ill effects have been proposed to result from vasoconstriction of the blood vessels supplying the uterus or interference with cell division in the developing fetus (Hinds et al., 1996). Consequently, caffeine-containing products, including caffeinated coffee, tea, soft drinks, and cocoa beverages, should be avoided or consumed only in limited quantities.

Aspartame (e.g., Nutrasweet, Equal) and acesulfame K (e.g., Sweet One), artificial sweeteners commonly used in low- or no-calorie beverages, have not been found to have adverse effects on the normal mother or fetus, but aspartame use should be avoided by pregnant women who are homozygous for phenylketonuria (PKU).

 

Minerals and Vitamins

In general, the nutrient needs of pregnant women, except perhaps the need for iron, can be met through dietary sources. Counseling about the need for a varied diet rich in vitamins and minerals should be a part of every pregnant woman's early prenatal care and should be reinforced throughout pregnancy. However, supplements of certain nutrients (listed in the following discussion) are recommended whenever the woman's diet is very poor or whenever significant nutritional risk factors are present. Nutritional risk factors in pregnancy are listed in Box 1.

 

BOX 1 Indicators of Nutritional Risk in Pregnancy Adolescence Frequent pregnancies: three within 2 years Poor fetal outcome in a previous pregnancy Poverty Poor diet habits with resistance to change Use of tobacco, alcohol, or drugs Weight at conception under or over normal weight Problems with weight gain Any weight loss Weight gain of less than 1 kg/mo after the first trimester Weight gain of more than 1 kg/wk after the first trimester Multifetal pregnancy Low hemoglobin or hematocrit values (or both)

 

Iron

Iron is needed both to allow for transfer of adequate iron to the fetus and to permit expansion of the maternal red blood cell (RBC) mass. Beginning in the latter part of the first trimester the blood volume of the mother increases steadily, peaking at approximately 1500 ml more than in the nonpregnant state. In twin gestations, the increase is at least 500 ml greater than in pregnancies with single fetuses. Plasma volume increases more than RBC mass. The relative excess of plasma causes a modest decrease in the hemoglobin concentration and hematocrit, known as physiologic anemia of pregnancy. This is a normal adaptation during pregnancy.

However, poor iron intake and absorption, which can result in iron deficiency anemia, is relatively common among women in the childbearing years. It affects nearly one fifth of the pregnant women in industrialized countries. The maternal mortality rate is increased among anemic women, who are poorly prepared to tolerate hemorrhage at the time of birth. In addition, anemic women may have a greater likelihood of cardiac failure during labor, postpartum infections, and poor wound healing. The fetus is also affected by maternal anemia. The risk of preterm birth is greater in anemic women, and fetal iron stores may also be reduced by maternal anemia (Allen, 2000). Anemia is more common among adolescents and African-American women than among adult Caucasian women.

Evidence supports the recommendation that all pregnant women receive a daily iron supplement (Allen, 2000). (Iron supplements may be poorly tolerated during the nausea that is prevalent in the first trimester.) If iron deficiency anemia (as manifested by low levels of hematocrit or hemoglobin and serum ferritin) is present, higher dosages are required. Certain foods taken with an iron supplement can promote or inhibit absorption of iron. Even when a woman is taking an iron supplement, she should include good food sources of iron in her daily diet (see Table 1).

 

Calcium

There is no increase in the DRI of calcium during pregnancy and lactation, in comparison with the recommendation for the nonpregnant woman (see Table 1). The DRI (1000 mg daily for women 19 and older and 1300 mg for those younger than 19) appears to provide sufficient calcium for fetal bone and tooth development to proceed while maintaining maternal bone mass.

Milk and yogurt are especially rich sources of calcium, providing approximately 300 mg per cup (240 ml). Nevertheless, many women do not consume these foods or do not consume adequate amounts to provide the recommended intakes of calcium. One problem that can interfere with milk consumption is lactose intolerance, the inability to digest milk sugar (lactose) caused by the absence of the lactase enzyme in the small intestine. Lactose intolerance is relatively common in adults, particularly African-Americans, Asians, Native Americans, and Eskimos. Milk consumption may cause abdominal cramping, bloating, and diarrhea in such people. Yogurt, sweet acidophilus milk, buttermilk, cheese, chocolate milk, and cocoa may be tolerated even when fresh fluid milk is not. Commercial products that contain the lactase enzyme (e.g., Lactaid) are available in pharmacies and many supermarkets. The lactase in these products hydrolyzes, or digests, the lactose in milk, making it possible for lactose-intolerant people to drink milk.

In some cultures, adults rarely drink milk. For example, Puerto Ricans and other Hispanic people may use it only as an additive in coffee. Pregnant women from these cultures may need to consume nondairy sources of calcium. Vegetarian diets may also be deficient in calcium (Box 2). If calcium intake appears low and the woman does not change her dietary habits despite counseling, a daily supplement containing 600 mg of elemental calcium may be needed. Calcium supplements may also be recommended when a pregnant woman experiences leg cramps caused by an imbalance in the calcium/phosphorus ratio.

 

BOX 2 Calcium Sources for Women Who Do Not Drink Milk Each of the following provides approximately the same amount of calcium as 1 cup of milk: FISH 3 oz can of sardines 4V2 oz can of salmon (if bones are eaten) BEANS AND LEGUMES 3 cups of cooked dried beans 2VS cups of retried beans 2 cups of baked beans with molasses 1 cup of tofu (calcium is added in processing) GREENS 1 cup of collards 1V2 cups of kale or turnip greens BAKED PRODUCTS 3 pieces of cornbread 3 English muffins 4 slices of French toast 2 (7 inch diameter) waffles FRUITS 11 dried figs 1V8 cups of orange juice with calcium added SAUCES 3 oz of pesto sauce 5 oz of cheese sauce

 

Sodium

During pregnancy the need for sodium increases slightly, primarily because the body water is expanding (e.g., the expanding blood volume). Sodium is essential for maintaining body water balance. Grain, milk, and meat products, which are good sources of nutrients needed during pregnancy, are significant sources of sodium.

In the past, dietary sodium was routinely restricted in n effort to control the peripheral edema that commonly occurs during pregnancy. However, it is now recognized that moderate peripheral edema is normal in pregnancy, occurring as a response to the fluid-retaining effects of elevated levels of estrogen. An excessive emphasis on sodium restriction may make it difficult for pregnant women to achieve an adequate diet. In addition, restriction of sodium intake may stress the adrenal glands and the kidney as they attempt to retain adequate sodium. In general, sodium restriction is necessary only if the woman has a medical condition such as renal or liver failure or hypertension.

Excessive intake of sodium is discouraged during pregnancy just as it is in nonpregnant women, because it may contribute to abnormal fluid retention and edema. Table salt (sodium chloride) is the richest source of sodium. Most canned foods contain added salt unless the label pecifically states otherwise. Large amounts of sodium are also found in many processed foods, including meats (e.g., smoked or cured meats, cold cuts, corned beef), baked goods, mixes for casseroles or grain products, soups, and condiments. Products low in nutritive value and excessively high in sodium include pretzels, potato and other chips, pickles, ketchup, prepared mustard, steak and Worcestershire sauces, some soft drinks, and bouillon. A moderate sodium intake can usually be achieved by salting food lightly in cooking, adding no additional salt at the table, and avoiding low-nutrient/high-sodium foods.

 

Zinc

Zinc is a constituent of numerous enzymes involved in major metabolic pathways. Zinc deficiency is associated with malformations of the central nervous system in infants. When large amounts of iron and folic acid are consumed, the absorption of zinc is inhibited and serum zinc levels are reduced as a result. Because iron and folic acid supplements are commonly prescribed during pregnancy, pregnant women should be encouraged to consume good sources of zinc daily (see Table 10-1). Women with anemia who receive high-dose iron supplements also need supplements of zinc (King, 2000).

 

Fluoride

The effect of prenatal fluoride supplementation on tooth development in the infant is not fully known. However, it appears that prenatal fluoride supplementation has little effect on the incidence and prevalence of tooth decay (Leverett et al., 1997). No increase in fluoride intake over the nonpregnant DRI is currently recommended during pregnancy (Standing Committee, 1997).

 

Fat-soluble vitamins

Fat-soluble vitamins (i.e., vitamins A, D, E, and K) are stored in the body tissues. With chronic overdoses, these vitamins can reach toxic levels. Because of the high potential for toxicity, pregnant women are advised to take fatsoluble vitamin supplements only as prescribed. Vitamins A and D deserve special mention.

Adequate intake of vitamin A is needed so that sufficient amounts can be stored in the fetus. However, dietary sources can readily supply sufficient amounts. Congenital malformations have occurred in infants of mothers who took excessive amounts of vitamin A during pregnancy, and thus supplements are not recommended for pregnant women. Vitamin A analogs such as isotretinoin (Accutane), which are prescribed for the treatment of cystic acne, are a special concern. Isotretinoin use during early pregnancy has been associated with an increased incidence of heart malformations, facial abnormalities, cleft palate, hydrocephalus, and deafness and blindness in the infant, as well as an increased risk of miscarriage. Topical agents such as tretinoin (Retin-A) do not appear to enter the circulation in any substantial amounts, but their safety in pregnancy has not been confirmed.

Vitamin D plays an important role in absorption and metabolism of calcium. The main food sources of this vitamin are enriched or fortified foods such as milk and ready-to-eat cereals. Vitamin D is also produced in the skin by the action of ultraviolet light (in sunlight). Severe deficiency may cause neonatal hypocalcemia and tetany, as well as hypoplasia of the tooth enamel. Women with lactose intolerance and those who do not include milk in their diet for any reason are at risk for vitamin D deficiency. Other risk factors are dark skin, habitual use of clothing that covers most of the skin, and living in northern latitudes where sunlight exposure is limited, especially during the winter.

 

Water-soluble vitamins

Body stores of water-soluble vitamins are much smaller than those of fat-soluble vitamins; the water-soluble vitamins, in contrast to fat-soluble vitamins, are readily excreted in the urine. Therefore good sources of water-soluble vitamins must be consumed frequently, and toxicity with overdose is less likely than with fat-soluble vitamins.

Because of the increase in RBC production during pregnancy, as well as the nutritional requirements of the rapidly growing cells in the fetus and placenta, pregnant women should consume approximately 50% more folic acid than nonpregnant women, or approximately 600 /jug daily. This increased need for folic acid continues during lactation (Bailey & Gregory, 1999). In the United States, all enriched grain products (this includes most white breads, flour, and pasta) must contain folic acid at a level of 1.4 mg per kilogram of flour. This level of fortification supplies approximately 0.1 mg of folic acid daily in the average American diet (USDHHS, FDA, 1996). All women of childbearing potential need careful counseling about including good sources of folic acid in their diet (Tinkle & Sterling, 1997).

Pyridoxine, or vitamin B6, is involved in protein metabolism. Although levels of a pyridoxine-containing enzyme have been reported to be low in women with pregnancyinduced hypertension, there is no evidence that supplementation prevents or corrects the condition. No supplement is recommended routinely, but women with poor diets and those at nutritional risk (see Box 1) may need a supplement. Supplementation is related to a lowered incidence of dental decay in pregnant women (Mahomed & Gulmezoglu, 2000).

Vitamin C, or ascorbic acid, plays an important role in tissue formation and enhances the absorption of iron. The vitamin C needs of most women are readily met by a diet that includes at least five servings per day of fruits and vegetables (Levine et al., 1999) (see Table 1), but women who smoke need more. For women at nutritional risk, a supplement is recommended. However, if the mother takes excessive doses of this vitamin during pregnancy, a vitamin C deficiency may develop in the infant after birth.

 

Nutrient supplements

Food can and should be the normal vehicle to meet the additional needs imposed by pregnancy (excepting iron, for which a supplemental dose is recommended). However, some women chronically consume diets that are deficient in necessary nutrients and, for whatever reason, may be unable to change this intake. For these women a supplement should be considered. It is important that the pregnant woman understand that the use of a vitamin/mineral supplement does not lessen the need to consume a nutritious, well-balanced diet.

 

OTHER NUTRITIONAL ISSUES DURING

PREGNANCY

Pica and food cravings

Pica is the practice of consuming nonfood substances (e.g., clay, dirt, laundry starch) or excessive amounts of foodstuffs low in nutritional value (e.g., cornstarch, ice, baking powder, soda). Pica is often influenced by the woman's cultural background. In the United States it appears to be most common among African-American women, women from rural areas, and women with a family history of pica. Regular and heavy consumption of low-nutrient products may cause more nutritious foods to be displaced from the diet, and the items consumed may interfere with the absorption of nutrients, especially minerals. Women with pica have lower hemoglobin levels than those without pica (Rainville, 1998). The possibility of pica must be considered when pregnant women are found to be anemic, and the nurse should provide counseling about the health risks associated with pica. The existence of pica, as well as details of the type and amounts of products ingested, is likely to be discovered only by the sensitive interviewer who has developed a relationship of trust with the woman. It has been proposed that pica and food cravings (e.g., the urge to consume ice cream, pickles, pizza) during pregnancy are caused by an innate drive to consume nutrients missing from the diet. However, research has not supported this hypothesis.

 

Adolescent pregnancy

Many adolescent females have diets that fall below the recommended intakes of key nutrients, including energy, calcium, and iron. Teens have lower BMIs than adults and are at risk for having babies of lower birth weight than adult women (Buschman, Foster, & Vickers, 2001).

Pregnant adolescents and their infants are at increased risk of complications during pregnancy and parturition. Growth of the pelvis is delayed in comparison to growth in stature, and this helps explain why cephalopelvic disproportion and other mechanical problems associated with labor are common among young adolescents. Competition between the growing adolescent and the fetus for nutrients may also contribute to some of the poor outcomes apparent in teen pregnancies. Pregnant adolescents are encouraged to choose a weight gain goal at the upper end of the range for their BMI (see Research box).

 

RESEARCH Weight Gain and Birth Weight in the Pregnant Young Teen The weight of newborns is correlated with immediate survival and with long-term health. Pregnancy in adolescence is especially vulnerable to a low-birthweight outcome, possibly because the adolescent starts pregnancy with a lower body mass index (BMI), has poor nutrition, or is still growing herself. Low birth weight for gestation indicates pathology of the fetus, mother, or placenta. Birth weight of the baby is dependent on weight gain of the mother during pregnancy. Girls 16 years of age and older share the same weight gain patterns and pregnancy outcomes as adult women. Younger teens, however, do not fit this pattern. Studying a region of Scotland with a high rate of teen pregnancy, researchers retrospectively compared 104 pregnant adolescents, ages 13 to 15 years, with a control group of 150 pregnant adults, ages 25 to 30 years. The researchers calculated the "prepregnancy BMI" based on weight and height at first visit up to 16 weeks of gestation. The "end-of-pregnancy BMI" calculation came from the original height and the recorded weight at 36 or more weeks of gestation. Analysis of the data confirmed that the adolescents started and ended pregnancy with lower BMIs than the adults. For both groups, a higher end-of-pregnancy BMI correlated to higher birth weights. Adolescents gained as much weight in proportion to body size as adult women, yet still delivered lower-birth-weight babies. It was noteworthy that 30% of the adolescents smoked, compared with 18% of adults, which also may have affected birth weight. IMPLICATIONS FOR PRACTICE Nurses who encounter young pregnant teens need to be aware of their special nutritional needs. Involving the nutritionist and the family members who prepare the meals may assist the teen in eating the right kinds of food for a healthy baby outcome. Referrals to special "Teen OB" clinics and peer support groups may provide conducive environments for teens to be educated about nutrition, smoking cessation, and the importance of preventing low-birth-weight babies. Source: Buschman, N., Foster, G., & Vickers, P. (2001). Adolescent girls and their babies: Achieving optimal birthweight. Gestational weight gain and pregnancy outcome in terms of gestation at delivery and infant birth weight: A comparision between adolescents under 16 and adult women. Child Care Health Dev, 27(1) 163-171.

 

NUTRIENT NEEDS DURING LACTATION

Nutritional needs during lactation are similar in many ways to those during pregnancy (see Table 1). Needs for energy (calories), protein, calcium, iodine, zinc, the B vitamins (thiamine, riboflavin, niacin, pyridoxine, and vitamin B12), and vitamin C remain elevated over nonpregnant needs. The recommendations for some of these (e.g., vitamin C, zinc, protein) are slightly to moderately higher than during pregnancy. This allowance covers the amount of the nutrient released in the milk, as well as the needs of the mother for tissue maintenance. In the case of iron and folk acid, the recommendation during lactation is lower than during pregnancy. Both of these nutrients are essential for RBC formation, and thus for maintaining the increase in the blood volume that occurs during pregnancy. With the decrease in maternal blood volume to nonpregnant levels after birth, maternal iron and folic acid needs also fall. Many lactating women experience a delay in the return of menses, and this also conserves blood cells and reduces iron and folic acid needs. It is especially important that the calcium intake be adequate; if it is not and the women does not respond to diet counseling, a supplement of 600 mg of calcium per day may be needed.

The recommended energy intake is an increase of 500 kcal more than the woman's nonpregnant intake. Lactating women should consume at least 1800 kcal/day; it is difficult to obtain adequate nutrients for maintenance of lactation at levels below that. Because of deposition of energy stores, the woman who has gained the optimal amount of weight during pregnancy is heavier after birth than at the beginning of pregnancy. As a result of the caloric demands of lactation, however, the lactating mother usually experiences a gradual but steady weight loss. Most women experience a rapid loss of several pounds during the first month postpartum whether or not they breastfeed. After the first month the average loss during lactation is 0.5 to 1.0 kg per month, and a woman who is overweight may be able to lose up to 2 kg without decreasing her milk supply.

Fluid intake must be adequate to maintain milk production, but the mother's level of thirst is the best guide to the right amount. There is no need to consume fluids in excess of the amount needed to satisfy thirst.

CARE MANAGEMENT

During pregnancy, nutrition plays a key role in achieving an optimum outcome for the mother and her unborn baby. Motivation to learn about nutrition is usually higher during pregnancy as parents strive to "do what's right for the baby." Optimal nutrition cannot eliminate all problems that may arise in pregnancy, but it does establish a good foundation for supporting the needs of the mother and her unborn baby.

 

Assessment and Nursing Diagnoses

Assessment is based on a diet history (a description of the woman's usual food and beverage intake and factors affecting her nutritional status, such as medications being taken and adequacy of income to allow her to purchase the necessary foods) obtained from an interview and re view of the woman's health records, physical examination, and laboratory results. Ideally, a nutritional assessment is performed before conception so that any recommended changes in diet, lifestyle, and weight can be undertaken before the woman becomes pregnant.

 

Diet history

Obstetric and gynecologic effects on nutrition. Nutritional reserves may be depleted in the multiparous woman or one who has had frequent pregnancies (especially three pregnancies within 2 years). A history of preterm birth or the birth of an LBW or SGA infant may indicate inadequate dietary intake. Pregnancy-induced hypertension may also be a factor in poor maternal nutrition. Birth of an infant who is large for gestational age may indicate maternal diabetes mellitus. Previous contraceptive methods also may affect reproductive health. Increased menstrual blood loss often occurs during the first 3 to 6 months after placement of an intrauterine contraceptive device. Consequently, the user may have low iron stores or even iron deficiency anemia. Oral contraceptive agents, on the other hand, are associated with decreased menstrual losses and increased iron stores; however, oral contraceptives may interfere with folic acid metabolism.

Medical history. Chronic maternal illnesses, such as diabetes mellitus, renal disease, liver disease, or cystic fibrosis, or other malabsorptive disorders, seizure disorders and the use of anticonvulsant agents, hypertension, and PKU may affect nutritional status and dietary needs. In women with illnesses that have resulted in nutritional deficits or that require dietary treatment (e.g., diabetes mellitus, PKU), it is extremely important for nutritional care to be started and for the condition to be optimally controlled before conception. A registered dietitian can provide in-depth counseling for the woman who requires a therapeutic diet during pregnancy and lactation.

Usual maternal diet. The woman's usual food and beverage intake, adequacy of income and other resources to meet her nutritional needs, any dietary modifications, food allergies and intolerances, and all medications and nutrition supplements being taken, as well as pica and cultural dietary requirements, should be ascertained. In addition, the presence and severity of nutrition-related discomforts of pregnancy, such as morning sickness, constipation, and pyrosis (heartburn), should be determined. The nurse should be alert to any evidence of eating disorders such as anorexia nervosa, bulimia, or frequent and rigorous dieting before or during pregnancy.

The impact of food allergies and intolerances on nutritional status ranges from very important to almost nil. Lactose intolerance is of special concern in pregnant and lactating women because no other food group equals milk and milk products in terms of calcium content. If a woman suffers from lactose intolerance, the interviewer should explore her intake of other calcium sources (see Box 2).

The assessment must include an evaluation of the woman's financial status and her knowledge of sound dietary practices. The quality of the diet increases with increasing socioeconomic status and educational level. Poor women may not have access to adequate refrigeration and cooking facilities and may find it difficult to obtain adequate nutritious food.

Herbal supplements. Specific questions about the use of botanicals (e.g., herbs and other "natural" remedies) should be included in the assessment (Hatcher, 2001). Whether the woman uses herbs as part of her culture or tradition should be ascertained; this will assist the nurse to determine the clinical significance of the use of herbs. The following questions can be included in the assessment (Hatcher, 2001):

• Have you used or considered using herbal or vitamin supplements?

• Have you recently had a symptom that over-the-counteror prescription medications did not relieve? Have you tried to find relief using an herbal remedy?

• Have you ever used the herbs feverfew, ginseng, or garlic? (These herbs prolong clotting times.)

• Do you combine herbal remedies with over-the-counter or prescription medications?

Box 3 provides a simple tool for obtaining diet history information. When potential problems are identified, they should be followed up with a careful interview. Women should be cautioned to avoid the use of herbs during pregnancy and lactation.

 

Box 3 Food Intake Questionnaire

 

 

Physical examination

Anthropometric measurements (body measurements, such as height and weight) provide both short- and longterm information on a woman's nutritional status and are thus essential to the assessment. At a minimum, the woman's height and weight must be determined at the time of her first prenatal visit and her weight should be measured at every subsequent visit (see earlier discussion of BMI).

A careful physical examination can reveal objective signs of malnutrition (Table 3). It is important to note, however, that some of these signs are nonspecific and that the physiologic changes of pregnancy may complicate the interpretation of physical findings. For example, lower extremity edema often occurs in calorie and protein deficiency, but it may also be a normal finding in the third trimester of pregnancy. Interpretation of physical findings is made easier by a thorough health history and by laboratory testing, if indicated.

 

 

 

Laboratory testing

The only nutrition-related laboratory testing needed by most pregnant women is a hematocrit or hemoglobin measurement to screen for the presence of anemia. Because of the physiologic anemia of pregnancy, the reference values for hemoglobin and hematocrit must be adjusted during pregnancy. The lower limit of the normal range for hemoglobin during pregnancy is 11 g/dl in the first and third trimesters and 10.5 g/dl in the second trimester (compared with 12 g/dl in the nonpregnant state). The lower limit of the normal range for hematocrit is 33% during the first and third trimesters and 32% in the second trimester (compared with 36% in the nonpregnant state). Cutoff values for anemia are higher in women who smoke or live at high altitudes, because the decreased oxygen-carrying capacity of their RBCs causes them to produce more RBCs than other women.

A woman's history or physical findings may indicate the need for additional testing, such as a complete blood cell count with a differential to identify megaloblastic or macrocytic anemia and measurement of levels of specific vitamins or minerals believed to be lacking in the diet.

The assessment gives a basis for making appropriate nursing diagnoses, such as the following.

• Imbalanced nutrition: less than body requirements related to

-inadequate information about nutritional needs and weight gain during pregnancy

-misperceptions regarding normal body changes during pregnancy and inappropriate fear of becoming fat

-inadequate income or skills in meal planning and preparation

• Imbalanced nutrition: more than body requirements related to

-excessive intake of energy (calories) or decrease in activity during pregnancy

-use of unnecessary dietary supplements

• Constipation related to

-decrease in gastrointestinal motility because of elevated progesterone levels

-compression of intestines by the enlarging uterus

-oral iron supplementation

 

EXPECTED OUTCOMES OF CARE

The nurse, dietitian, physician, and nurse-midwife collaborate with the woman in helping her achieve nutrition-related expected outcomes. Some common nutrition-related outcomes are that the woman will take the following actions:

• Achieve an appropriate weight gain during pregnancy. An appropriate goal for weight gain takes into account such factors as prepregnancy weight, whether she is overweight/obese or underweight, and whether the pregnancy is single or multifetal.

• Consume adequate nutrients from the diet and supplements to meet estimated needs.

• Cope successfully with nutrition-related discomforts associated with pregnancy, such as morning sickness, pyrosis (heartburn), and constipation.

 

PLAN OF CARE AND INTERVENTIONS

Nutritional care and teaching generally involve (1) acquainting the woman with nutritional needs during pregnancy and, if necessary, the characteristics of an adequate diet; (2) helping her individualize her diet so that she achieves an adequate intake while satisfying her personal, cultural, financial, and health needs; (3) acquainting her with strategies for coping with the nutrition-related discomforts of pregnancy; (4) helping the woman use nutrition supplements appropriately; and (5) consulting with and making referrals to other professionals or services as indicated. Two programs that provide nutrition services are the food stamp program and the Special Supplemental Program for Women, Infants, and Children (WIC). These programs provide vouchers for selected foods to pregnant and lactating women, as well as infants and children at nutritional risk. WIC foods include items such as eggs, cheese, milk, juice, and fortified cereals; these foods are chosen because they provide iron, protein, vitamin C, and other vitamins.

Adequate dietary intake

Diet teaching can take place in a one-on-one interview or in a group setting. In either case it should emphasize the importance of choosing a varied diet composed of readily available foods, rather than specialized diet supplements. Good nutrition practices and avoidance of poor practices (e.g., smoking, alcohol or drug use) are essential content for prenatal classes designed for women in early pregnancy.

The food guide pyramid (Fig. 4) can be used as a guide to daily food choices during pregnancy and lactation, just as it is during other stages of the life cycle. The importance of consuming adequate amounts from the milk, yogurt, and cheese group must be emphasized, especially for adolescents and women younger than 25 years of age, who are still actively adding calcium to their skeletons; adolescents need at least 1 L of milk or the equivalent daily.

 

 

Fig. 4 Food guide pyramid, a guide to daily food choices. (Courtesy U.S. Department of Agriculture, Washington, DC.)

 

Pregnancy. The pregnant woman must understand what adequate weight gain during pregnancy means, must recognize the reasons for its importance, and must be able to evaluate her own gain in relation to the desirable pattern. Many women, particularly those who have worked hard to control their weight before pregnancy, may find it difficult to understand why the weight gain goal is so high when a newborn infant is so small. The nurse can explain that maternal weight gain consists of increments in the weight of many tissues, not just the growing fetus.

On the other hand, dietary overindulgence, which may result in excessive fat stores that persist after giving birth, should be discouraged. Nevertheless, it is best not to focus unduly on weight gain; this can result in feelings of stress and guilt in the woman who does not follow the preferred pattern of gain.

Postpartum. The need for a varied diet with portions of food from all food groups continues throughout lactation. As mentioned previously, the lactating woman should be advised to consume at least 1800 kcal daily, and she should receive counseling if her diet appears to be inadequate in any nutrients. Special attention should be given to her intake of zinc, vitamin B6, and folic acid because the recommendations for these remain higher than those for nonpregnant women (see Table 1). Sufficient calcium is needed to allow for both milk formation and maintenance of maternal bone mass. It may be difficult for lactating women to consume enough of these nutrients without careful diet planning.

The woman who does not breastfeed loses weight gradually if she consumes a balanced diet that provides slightly less than her daily energy expenditure. Lactating and nonlactating women should know that fat is the most concentrated source of calories in the diet (9 kcal/g versus 4 kcal/g in carbohydrates and proteins), and fat calories are more efficiently converted into fat stores than are calories from carbohydrate or protein. Therefore the first step in weight reduction (or controlling excessive weight gain) is to evaluate sourse of fat in the diet and explore with the patient ways of reducing them. Even foods such as vegetables that are naturally low in fat can become high in fat when fried or sauteed, served with excessive amounts of salad dressing, consumed with high-fat dips or sauces, or seasoned with butter or bacon drippings. A reasonable weight loss goal for nonlactating women is 0.5 to 1.0 kg/wk; a loss of 1.0 kg/mo is recommended for most lactating women who need to lose weight.

Daily food guide and menu planning. The daily food plan (see Table 2 and Fig. 10-4) can be used as a guide for educating women about nutritional needs during pregnancy and lactation. This food plan is general enough to be used by women from a variety of cultures, including those following a vegetarian diet. One of the more helpful teaching strategies is to assist the patient to plan daily menus that follow the food plan and are affordable, have realistic preparation times, and are compatible with personal preferences and cultural practices. Information regarding cultural food patterns is provided later in this chapter.

Therapeutic diets. During pregnancy and lactation, the food plan for women with special therapeutic diets may need to be modified. The registered dietitian can instruct these women about their diets and assist them in meal planning. However, the nurse should understand the basic principles of the diet and be able to reinforce the diet teaching.

The nurse should be especially aware of the dietary modifications necessary for women with diabetes mellitus (either gestational or preexisting) because this disease is relatively common and because fetal deformity and death occur more often in pregnancies complicated by hyperglycemia or hypoglycemia. Every effort should be made to maintain blood glucose levels in the normal range throughout pregnancy. The food plan of the woman with diabetes usually includes four to six meals and snacks daily, with the daily carbohydrate intake distributed fairly evenly among those meals and snacks. The complex carbohydrates (i.e., fibers and starches) should be well represented in the diet of the woman with diabetes. See Chapter 22 for a discussion of the woman with diabetes.

 

Iron supplementation

As mentioned earlier, the nutritional supplement most commonly needed during pregnancy is iron. However, a variety of dietary factors can affect the completeness of absorption of an iron supplement. The following points should be addressed in patient education:

• Bran, milk, egg yolks, coffee, tea, or oxalate-containing vegetables such as spinach and Swiss chard consumed at the same time as iron will inhibit iron absorption.

• Iron absorption is promoted by a diet rich in vitamin C (e.g., citrus fruits or melons) or "heme iron" found in red meats, fish, and poultry.

• Iron supplements are best absorbed on an empty stomach; thus they can be taken between meals with beverages other than milk, tea, or coffee.

• Some women have gastrointestinal discomfort when they take the supplement on an empty stomach; therefore a good time for them to take the supplement is just before bedtime.

• Constipation is common with iron supplementation.

• Iron supplements should be kept away from any children in the household because their ingestion could result in acute iron poisoning and even death.

 

Coping with nutrition-related discomforts of pregnancy

The most common nutrition-related discomforts of pregnancy are nausea and vomiting or "morning sickness," constipation, and pyrosis.

Nausea and vomiting. Nausea and vomiting are most common during the first trimester. Usually, nausea and vomiting cause only mild to moderate problems nutritionally, although they may cause substantial discomfort. Antiemetic medications, vitamin B6, and P6 acupressure may be effective in reducing the severity of nausea (Jewell & Young, 2000). The pregnant woman may find the following suggestions helpful in alleviating the problem:

• Eat dry, starchy foods such as dry toast, Melba toast, or crackers on awakening in the morning and at other times when nausea occurs.

• Avoid consuming excessive amounts of fluids early in the day or when nauseated (but compensate by drinking fluids at other times).

• Eat small amounts frequently (every 2 to 3 hours) and avoid large meals, which distend the stomach.

• Avoid skipping meals and thus becoming extremely hungry, which may worsen nausea. Have a snack such as cereal with milk, a small sandwich, or yogurt before bedtime.

• Avoid sudden movements. Arise from bed slowly.

• Decrease intake of fried and other fatty foods. Starches (e.g., pastas, rice, breads) and low-fat protein foods (e.g., skinless broiled or baked poultry, cooked dry beans or peas, lean meats, broiled or canned fish) are good choices.

• Some women find that tart foods or drinks (e.g., lemonade) or salty foods (e.g., potato chips) are tolerated during periods of nausea.

• Herbal teas such as those made with raspberry leaf or peppermint may decrease nausea.

• Fresh air may help relieve nausea. Keep the environment well ventilated (e.g., open a window), go for a walk outside, or decrease cooking odors by using an exhaust fan.

• During periods of nausea, eat foods served at cool temperature and foods that give off little aroma.

• Avoid brushing teeth immediately after eating.

Hyperemesis gravidarum (i.e., severe and persistent vomiting causing weight loss, dehydration, and electrolyte abnormalities) occurs in up to 1% of pregnant women. 4f k) There is some evidence that ginger root may be effective in reducing nausea (Jewell & Young, 2000). Intravenous fluid and electrolyte replacement is usually necessary for women who lose 5% of their body weight. This is often followed by improved tolerance of oral intake; therapy then consists of frequently consuming small amounts of low-fat foods. Tube feedings may be used to supplement oral intake, with the volume of the tube feeding gradually being decreased as oral intake improves. In some instances, total parenteral nutrition (balanced intravenous feedings of amino acids, carbohydrate, lipid, vitamins, and minerals) is used to nourish women with hyperemesis gravidarum when their nutritional status is severely impaired.

Constipation. Improved bowel function generally results when the intake of fiber (e.g., wheat bran and wholewheat products, popcorn, raw or lightly steamed vegetables) in the diet is increased because fiber helps retain water within the stool, creating a bulky stool that stimulates intestinal peristalsis. The recommendation for adults for fiber is 25 to 30 g/day. An adequate fluid intake (at least 50 ml/kg/day) helps hydrate the fiber and increase the bulk of the stool. Making a habit of regular exercise that uses large muscle groups (walking, swimming, cycling) also helps stimulate bowel motility.

Pyrosis. Pyrosis, or heartburn, is usually caused by reflux of gastric contents into the esophagus. This condition can be minimized by eating small, frequent meals rather than two or three larger meals daily. Because fluids increase the distention of the stomach, they should not be consumed with foods. The woman needs to be sure to drink adequate amounts between meals. Avoiding spicy foods may help alleviate the problem. Lying down immediately after eating and wearing clothing that is tight across the abdomen can contribute to the problem of reflux.

 

Cultural influences

Consideration of a woman's cultural food preferences enhances communication and provides a greater opportunity for following the agreed-on pattern of intake. Women in most cultures are encouraged to eat a diet typical for them. The nurse needs to be aware of what constitutes a typical diet for each cultural or ethnic group with whom she works. However, several variations may occur within one cultural group. Thus careful exploration of individual preferences is needed. Although ethnic and cultural food beliefs may seem, at first glance, to conflict with the dietary instruction provided by physicians, nurses, and dietitians, it is often possible for the empathic health care provider to identify cultural beliefs that are congruent with the modern understanding of pregnancy and fetal development. Many cultural food practices have some merit or the culture would not have survived. Food cravings during pregnancy are considered normal by many cultures, but the kinds of cravings often are culturally specific. In most cultures women crave acceptable foods, such as chicken, fish, and greens among African-Americans. Cultural influences on food intake usually lessen if the woman and her family become more integrated into the dominant culture. Nutrition beliefs and the practices of selected cultural groups are summarized in Table 4.

 

Table 4 Characteristic Food Patterns of Selected Cultures

 

Vegetarian diets

Vegetarian diets represent another cultural effect on nutritional status. Foods basic to almost all vegetarian diets are vegetables, fruits, legumes, nuts, seeds, and grains. However, there are many variations in vegetarian diets. Semivegetarians, who are not truly vegetarians, include fish, poultry, eggs, and dairy products in their diets but do not eat beef or pork. Such a diet can be completely adequate for pregnant women. Besides plant products, lactoovovegetarians also eat dairy products. Iron and zinc intake may not be adequate in these women, but such diets can be otherwise nutritionally sound. Strict vegetarians, or vegans, consume only plant products. Because vitamin B12 is found only in foods of animal origin, this diet is therefore deficient in vitamin B12. As a result, strict vegetarians should take a supplement or consume vitamin B12-fortified foods (e.g., soy milk) regularly. Vitamin B,2 deficiency can result in megaloblastic anemia, glossitis, and neurologic deficits in the mother. Infants born to affected mothers are likely to have megaloblastic anemia and exhibit neurodevelopmental delays. Iron, calcium, zinc, and vitamin B6 intake may also be low in women on this diet, and some strict vegetarians have excessively low caloric intakes. The protein intake should be assessed especially carefully because plant proteins tend to be incomplete, in that they lack one or more amino acids required for growth and the maintenance of body tissues. The daily consumption of a variety of different plant proteins (e.g., grains, dried beans and peas, nuts, seeds) helps provide all the essential amino acids.

 

EVALUATION

When weight gain is inadequate or nutritional deficits appear, the nurse must assess the woman and her understanding of her nutritional needs, reinforce teaching as needed, and continue to reevaluate regularly (see Plan of Care).

 

PLAN OF CARE Nutrition During Pregnancy

NURSING DIAGNOSIS Deficient knowledge related to nutritional requirements during pregnancy

Expected Outcome The patient will delineate nutritional requirements and exhibit evidence of incorporating requirements into diet.

Nursing Interventions/Rationales

Review basic nutritional requirements for a healthy diet using recommended dietary guidelines and the food guide pyramid to provide knowledge baseline for discussion.

Discuss increased nutrient needs (calories, protein, minerals, vitamins) that occur as a result of being pregnant to increase knowledge needed for altered dietary requirements.

Discuss the relationship between weight gain and fetal growth to reinforce interdependence of fetus and mother.

Calculate the appropriate total weight gain range during pregnancy using the woman's body mass index as a guide and discuss recommended rates of weight gain during the various trimesters of pregnancy to provide concrete measures of dietary success.

Review food preferences, cultural eating patterns or beliefs, and prepregnancy eating patterns to enhance integration of new dietary needs.

Discuss how to fit nutritional needs into usual dietary patterns and how to alter any identified nutritional deficits or excesses to increase chances of success with dietary alterations.

Discuss food aversions or cravings that may occur during pregnancy and strategies to deal with these if they are detrimental to fetus (e.g., pica) to ensure well-being of fetus.

Have woman keep a food diary delineating eating habits, dietary alterations, aversions, and cravings to track eating habits and potential problem areas.

 

NURSING DIAGNOSIS Imbalanced nutrition: more than body requirements related to excessive intake and/or inadequate activity levels

Expected Outcome The patient's weekly weight gain will be reduced to the appropriate rate using her body mass index (BMI) and recommended weight gain ranges as guidelines.

Nursing Interventions/Rationales

Review recent diet history (including food cravings) using a food diary, 24-hour recall, or food frequency approach to ascertain food excesses contributing to excess weight gain.

Review normal activity and exercise routines to determine level of energy expenditure; discuss eating patterns and reasons that lead to increased food intake (e.g., cultural beliefs or myths, increased stress, boredom) to identify habits that contribute to excess weight gain.

Review optimal weight gain guidelines and their rationale to ensure that the woman is knowledgeable about healthful weight gain rates.

Set target weight gains for the remaining weeks of the pregnancy to establish set goals.

Discuss with the woman what changes can be made in diet, activity, and lifestyle to enhance chances of meeting weight gain goals and dietary needs. Weight reduction diets should be avoided, since they may deprive the mother and fetus of needed nutrients and lead to ketonemia.

 

NURSING DIAGNOSIS (mbalanced nutrition: less than body requirements related to inadequate intake of needed nutrients

Expected Outcome The patient's weekly weight gain will be increased to the appropriate rate using her BMI and recommended weight gain ranges as guidelines.

Nursing Interventions/Rationales

Review recent diet history (including food aversions) using a food diary, 24-hour recall, or food frequency approach to ascertain dietary inadequacies contributing to lack of sufficient weight gain.

Review normal activity and exercise routines to determine level of energy expenditure; discuss eating patterns and reasons that lead to decreased food intake (e.g., morning sickness, pica, fear of becoming fat, stress, boredom) to identify habits that contribute to inadequate weight gain.

Review optimal weight gain guidelines and their rationale to ensure that woman is knowledgeable about healthful weight gain rates.

Set target weight gains for the remaining weeks of the pregnancy to establish set goals.

Review increased nutrient needs (calories, protein, minerals, vitamins) that occur as a result of being pregnant to ensure woman is knowledgeable about altered dietary requirements.

Review relationship between weight gain and fetal growth to reinforce that adequate weight gain is needed to promote fetal well-being.

Discuss with woman what changes can be made in diet, activity, and lifestyle to enhance chances of meeting set weight gain goals and nutrient needs of mother and fetus.

If woman has fear of being fat, if symptoms of an eating disorder are evident, or if problems in adjusting to a changing body image surface, refer woman to the appropriate mental health professional for evaluation, since intensive treatment and follow-up may be required to ensure maternal and fetal health.