UNIT TEST II
Prepared by assistant professor N.Petrenko, MD, PhD
Summarize knowledge about normal and complicated labour
During late pregnancy, the woman and fetus prepare for the labor process. The fetus has grown and developed in preparation for extrauterine life. The woman has undergone various physiologic adaptations during pregnancy that prepare her for birth and motherhood. Labor and birth represent the end of pregnancy, the beginning of extrauterine life for the newborn, and a change in the lives of the family. This chapter discusses the factors affecting labor, the process involved, the normal progression of events, and the adaptations made by both the woman and fetus.
FACTORS AFFECTING LABOR
At least five factors affect the process of labor and birth. These are easily remembered as the five P's: passenger (fetus and placenta), passageway (birth canal), powers (contractions), position of the mother, and psychologic response. The first four factors are presented here as the basis of understanding the physiologic process of labor. The fifth factor is discussed in Chapter 12. Other factors such as place of birth, preparation, type of provider, and procedures implemented may be important as well (VandeVusse, 1999).
The way the passenger, or fetus, moves through the birth canal is determined by several interacting factors: the size of the fetal head, fetal presentation, fetal lie, fetal attitude, and fetal position. Because the placenta must also pass through the birth canal, it can be considered a passenger along with the fetus. However, the placenta rarely impedes the process of labor in normal vaginal birth, except in cases of placenta previa.
Size of the fetal head
Fig. 1 Fetal head at term. A, Bones. B, Sutures and fontanels
Because of its size and relative rigidity, the fetal head has a major effect on the birth process. The fetal skull is composed of two parietal bones, two temporal bones, the frontal bone, and the occipital bone (Fig. 1, A). These bones are united by membranous sutures: the sagittal, lambdoidal, coronal, and frontal (Fig. 1, B). Membranefilled spaces called fontanels are located where the sutures intersect. During labor, after rupture of membranes, palpation of fontanels and sutures during vaginal examination reveals fetal presentation, position, and attitude.
The two most important fontanels are the anterior and posterior ones (see Fig. 1, B). The larger of these, the anterior fontanel, is diamond shaped, is approximately 3 by 2 cm in size, and lies at the junction of the sagittal, coronal, and frontal sutures. It closes by 18 months after birth. The posterior fontanel lies at the junction of the sutures of the two parietal bones and the one occipital bone, is triangular in shape, and is approximately 1 by 2 cm in size. It closes 6 to 8 weeks after birth.
Sutures and fontanels make the skull flexible to accommodate the infant brain, which continues to grow for some time after birth. Because the bones are not firmly united, however, slight overlapping of the bones, or molding of the shape of the head, occurs during labor. This capacity of the bones to slide over one another also permits adaptation to the various diameters of the maternal pelvis. Molding can be extensive, but the heads of most newborns assume their normal shape within 3 days of birth.
Although the size of the fetal shoulders may affect passage, their position can be altered relatively easily during labor; therefore one shoulder may occupy a lower level than the other. This creates a shoulder diameter that is smaller than the skull, facilitating passage through the birth canal. The circumference of the fetal hips is usually small enough not to create problems.
Fig. 2 Examples of fetal vertex (occiput) presentations in relation to front, back, or side of maternal pelvis.
Fig. 3 Fetal presentations. A-C, Breech (sacral) presentation. D, Shoulder presentation.
Presentation refers to the part of the fetus that enters the pelvic inlet first and leads through the birth canal during labor at term. The three main presentations are cephalic presentation (head first), occurring in 96% of births (Fig. 2); breech presentation (buttocks or feet first), occurring in 3% of births (Fig. 3, A-C); and shoulder presentation, seen in 1% of births (Fig. 3, D). Presenting part refers to that part of the fetal body first felt by the examining finger during a vaginal examination. In a cephalic presentation, the presenting part is usually the occiput; in a breech presentation, it is the sacrum; in the shoulder presentation, it is the scapula. When the presenting part is the occiput, the presentation is noted as vertex (see Fig. 2). Factors that determine the presenting part include fetal lie, fetal attitude, and extension or flexion of the fetal head.
Lie is the relationship of the long axis (spine) of the fetus to the long axis (spine) of the mother. There are two primary lies: longitudinal, or vertical, in which the long axis of the fetus is parallel with the long axis of the mother (see Fig. 11-2); and transverse, horizontal, or oblique, in which the long axis of the fetus is at a right angle diagonal to the long axis of the mother (see Fig. 3, D). Longitudinal lies are either cephalic or breech presentations, depending on the fetal structure that first enters the mother's pelvis. Vaginal birth cannot occur when the fetus stays in a transverse lie. An oblique lie is less common and usually converts to a longitudinal or transverse lie during labor (Cunningham et al., 2001).
Fig. 4 Diameters of the fetal head at term. A, Cephalic presentations: occiput, vertex, and sinciput; and cephalic diameters: suboccipitobregmatic, occipitofrontal, and occipitomental. B, Biparietal diameter.
Fig. 5 Head entering pelvis. Biparietal diameter is indicated with shading (9.25 cm). A, Suboccipitobregmatic diameter: complete flexion of head on chest so that smallest diameter enters. B, Occipitofrontal diameter: moderate extension (military attitude) so that large diameter enters. C, Occipitomental diameter: marked extension (deflection) so that largest diameter, which is too large to permit head to enter pelvis, is presenting.
Attitude is the relationship of the fetal body parts to each other. The fetus assumes a characteristic posture (attitude) in utero partly because of the mode of fetal growth and partly because of the way the fetus conforms to the shape of the uterine cavity. Normally, the back of the fetus is rounded so that the chin is flexed on the chest, the thighs are flexed on the abdomen, and the legs are flexed at the knees. The arms are crossed over the thorax, and the umbilical cord lies between the arms and the legs. This attitude is termed general flexion (see Fig. 2).
Deviations from the normal attitude may cause difficulties in childbirth. For example, in a cephalic presentation, the fetal head may be extended or flexed in a manner that presents a head diameter that exceeds the limits of the maternal pelvis, leading to prolonged labor, forceps- or vacuum-assisted birth, or cesarean birth.
Certain critical diameters of the fetal head are usually measured. The biparietal diameter, which is approximately 9.25 cm at term, is the largest transverse diameter and an important indicator of fetal head size (Fig. 4, B). In a well-flexed cephalic presentation, the biparietal diameter will be the widest part of the head entering the pelvic inlet. There are several anteroposterior diameters, but the smallest and the most critical one is the suboccipitobregmatic diameter (approximately 9.5 cm at term). When the head is in complete flexion, this diameter allows the fetal head to pass through the true pelvis easily (Figs. 4, A, and 5, A). As the head is more extended, the anteroposterior diameter widens and the head may not be able to enter the true pelvis (Fig. 5, B and C).
The presentation or presenting part indicates that portion of the fetus that overlies the pelvic inlet. Position is the relationship of the presenting part (occiput, sacrum, mentum [chin], or sinciput [deflexed vertex]) to the four quadrants of the mother's pelvis (see Fig. 2). Position is denoted by a three-letter abbreviation. The first letter of the abbreviation denotes the location of the presenting part in the right (R) or left (L) side of the mother's pelvis. The middle letter stands for the specific presenting part of the fetus (0 for occiput, S for sacrum, M for mentum [chin], and Sc for scapula [shoulder]). The third letter stands for the location of the presenting part in relation to the anterior (A), posterior (P), or transverse (T) portion of the maternal pelvis. For example, ROA means that the occiput is the presenting part and is located in the right anterior quadrant of the maternal pelvis (see Fig. 2). LSP means that the sacrum is the presenting part and is located in the left posterior quadrant of the maternal pelvis (see Fig. 3).
Fig. 6 Stations of presenting part, or degree of descent. Biparietal diameter of the fetal head is just below the level of the ischial spines, between station 0 and station +1.
Station is the relationship of the presenting part of the fetus to an imaginary line drawn between the maternal ischial spines and is a measure of the degree of descent of the presenting part of the fetus through the birth canal. The placement of the presenting part is measured in centimeters above or below the ischial spines (Fig. 6). For example, when the lowermost portion of the presenting part is 1 cm above the spines, it is noted as being minus (—) 1. At the level of the spines, the station is referred to as 0 (zero). When the presenting part is 1 cm below the spines, the station is said to be plus (+) 1. Birth is imminent when the presenting part is at +4 to +5 cm. The station of the presenting part should be determined when labor begins so that the rate of descent of the fetus during labor can be accurately determined.
Engagement is the term used to indicate that the largest transverse diameter of the presenting part (usually the biparietal diameter) has passed through the maternal pelvic brim or inlet into the true pelvis and usually corresponds to station 0. Engagement often occurs in the weeks just before labor begins in primigravidas and may occur before labor or during labor in multigravidas. Engagement can be determined by abdominal or vaginal examination.
The passageway, or birth canal, is composed of the mother's rigid bony pelvis and the soft tissues of the cervix, pelvic floor, vagina, and introitus (the external opening to the vagina). Although the soft tissues, particularly the muscular layers of the pelvic floor, contribute to vaginal birth of the fetus, the maternal pelvis plays a far greater role in the labor process because the fetus must successfully accommodate itself to this relatively rigid passageway. Therefore the size and shape of the pelvis must be determined before childbirth begins.
Fig . 7 Female pelvis. A, Pelvic brim above. B, Pelvic outlet from below.
The anatomy of the bony pelvis is described in Chapter 4. The following discussion focuses on the importance of pelvic configurations as they relate to the labor process. (It may be helpful to refer to Fig. 4.)
The bony pelvis is formed by the fusion of the ilium, ischium, pubis, and sacral bones. The four pelvic joints are the symphysis pubis, the right and left sacroiliac joints, and the sacrococcygeal joint (Fig. 7, A). The bony pelvis is separated by the brim, or inlet, into two parts: the false pelvis and the true pelvis. The false pelvis is that part above the brim and plays no part in childbearing. The true pelvis, that part involved in birth, is divided into three planes: the inlet, or brim; the midpelvis, or cavity; and the outlet.
The pelvic inlet, which is the upper border of the true pelvis, is formed anteriorly by the upper margins of the pubic bone, laterally by the iliopectineal lines along the innominate bones, and posteriorly by the anterior, upper margin of the sacrum and the sacral promontory.
The pelvic cavity, or midpelvis, is a curved passage having a short anterior wall and a much longer concave posterior wall. It is bounded by the posterior aspect of the symphysis pubis, the ischium, a portion of the ilium, the sacrum, and the coccyx.
The pelvic outlet is the lower border of the true pelvis. Viewed from below, it is ovoid, somewhat diamond shaped, bounded by the pubic arch anteriorly, the ischial tuberosities laterally, and the tip of the coccyx posteriorly (Fig. 7, B). In the latter part of pregnancy the coccyx is movable (unless it has been broken in a fall during skiing or skating, for example, and has fused to the sacrum during healing).
Fig. 8 Pelvic cavity. A, Inlet and midplane. Outlet not shown. B, Cavity of true pelvis. C, Note curve of sacrum and axis of birth canal.
The pelvic canal varies in size and shape at various levels. The diameters at the plane of the pelvic inlet, midpelvis, and outlet, plus the axis of the birth canal (Fig. 8), determine whether vaginal birth is possible and the manner by which the fetus may pass down the birth canal.
The subpubic angle, which determines the type of pubic arch, together with the length of the pubic rami and the intertuberous diameter, is of great importance. Because the fetus must first pass beneath the pubic arch, a narrow subpubic angle will be less accommodating than a rounded, wide arch. The method of measurement of the subpubic arch is shown in Fig. 9. A summary of obstetric measurements is given in Table 1.
Fig. 9 Estimation of angle of subpubic arch. Using both thumbs, examiner externally traces descending ramidown to tuberosities. (From Barkauskas, V., Baumann, L, & Darling-Fisher, C. , Health and physical assessment [3rd ed.]. St. Louis: Mosby.)
Table 1 Obstetric Measurements
Inlet (superior strait)
Obstetric: measurement that determines whether presenting part can engage or enter superior strait
True (vera) (anteroposterior)
1.5-2 cm less than diagonal
≥ 11 cm (12.5) (radiographic)
Length of diagonal conjugate (solid colored line), obstetric conjugate (broken colored line), and true conjugate (black line)*
Transverse diameter (interspinous diameter)
The midplane of the pelvis normally is its largest plane and the one of greatest diameter.
Measurement of interspinous diameter*
Transverse diameter (intertuberous diameter) (biischial)
The outlet presents the smallest plane of the pelvic canal.
Use of Thorn's pelvimeter to measure
The four basic types of pelvis are classified as follows:
1. Gynecoid (the classic female type)
2. Android (resembling the male pelvis)
3. Anthropoid (resembling the pelvis of anthropoid apes)
4. Platypelloid (the flat pelvis)
The gynecoid pelvis is the most common, with major gynecoid pelvic features present in 50% of all women. Anthropoid and android features are less common, and platypelloid pelvic features are the least common. Mixed types of pelves are more common than pure types (Cunningham et al., 2001). Examples of pelvic variations and their effects on mode of birth are given in Table 2.
TABLE 2 Comparison of Pelvic Types
Assessment of the bony pelvis can be performed during the first prenatal evaluation and need not be repeated if the pelvis is of adequate size and suitable shape. In the third trimester of pregnancy, the examination of the bony pelvis may be more thorough and the results more accurate because there is relaxation and increased mobility of the pelvic joints and ligaments due to hormonal influences. Widening of the joint of the symphysis pubis and the resulting instability may cause pain in any or all of the pelvic joints.
Because the examiner does not have direct access to the bony structures and because the bones are covered with varying amounts of soft tissue, estimates of size and shape are approximate. Precise bony pelvis measurements can be determined by use of computed tomography, ultrasound, or x-ray films. However, x-ray examination is rarely done during pregnancy because the x-rays may damage the developing fetus.
The soft tissues of the passageway include the distensible lower uterine segment, cervix, pelvic floor muscles, vagina, and introitus. Before labor begins, the uterus is composed of the uterine body (corpus) and cervix (neck). After labor has begun, uterine contractions cause the uterine body to have a thick and muscular upper segment and a thin-walled, passive, muscular lower segment. A physiologic retraction ring separates the two segments (Fig. 10). The lower uterine segment gradually distends to accommodate the intrauterine contents as the wall of the upper segment thickens and its accommodating capacity is reduced. The contractions of the uterine body thus exert downward pressure on the fetus, pushing it against the cervix.
The cervix effaces (thins) and dilates (opens) sufficiently to allow the first fetal portion to descend into the vagina. As the fetus descends, the cervix is actually drawn upward and over this first portion.
Fig. 10 Uterus in normal labor in early first stage (A) and in second stage (B). Passive segment is derived from lower uterine segment (isthmus) and cervix, and physiologic retraction is derived from anatomic internal os. C, Uterus in abnormal labor in second-stage dystocia. Pathologic retraction (Bandl's) ring that forms under abnormal conditions develops from the physiologic ring.
The pelvic floor is a muscular layer that separates the pelvic cavity above from the perineal space below. This structure helps the fetus rotate anteriorly as it passes through the birth canal. As noted earlier, the soft tissues of the vagina develop throughout pregnancy until at term the vagina can dilate to accommodate the fetus and permit passage of the fetus to the external world.
Involuntary and voluntary powers combine to expel the fetus and the placenta from the uterus. Involuntary uterine contractions, termed the primary powers, signal the beginning of labor. Once the cervix has dilated, voluntary bearingdown efforts by the woman, termed the secondary powers, augment the force of the involuntary contractions.
The involuntary contractions originate at certain pacemaker points in the thickened muscle layers of the upper uterine segment. From the pacemaker points, contractions move downward over the uterus in waves, separated by short rest periods. Terms used to describe these involuntary contractions include frequency (the time from the beginning of one contraction to the beginning of the next), duration (length of contraction), and intensity (strength of contraction).
The primary powers are responsible for the effacement and dilation of the cervix and descent of the fetus. Effacement of the cervix means the shortening and thinning of the cervix during the first stage of labor. The cervix, normally 2 to 3 cm long and approximately 1 cm thick, is obliterated or "taken up" by a shortening of the uterine muscle bundles during the thinning of the lower uterine segment that occurs in advancing labor. Only a thin edge of the cervix can be palpated when effacement is complete. Effacement generally is advanced in first-time term pregnancy before more than slight dilation occurs. In subsequent pregnancies, effacement and dilation of the cervix tend to progress together. Degree of effacement is expressed in percentages from 0% to 100% (e.g., a cervix is 50% effaced) (Fig. 11, A-Q.
Fig. 11 Cervical effacement and dilation. Note how cervix is drawn up around presenting part (internal os). Membranes are intact and head is not well applied to cervix. A, Before labor. B, Early effacement. C, Complete effacement (100%). Head is well applied to cervix. D, Complete dilation (10 cm). There is some overlapping of cranial bones and membranes are still intact.
Dilation of the cervix is the enlargement or widening of the cervical opening and the cervical canal that occurs once labor has begun. The diameter of the cervix increases from less than 1 cm to full dilation (approximately 10 cm) to allow birth of a term fetus. When the cervix is fully dilated (and completely retracted), it can no longer be palpated (Fig. 11, D). Full cervical dilation marks the end of the first stage of labor.
Dilation of the cervix occurs by the drawing upward of the musculofibrous components of the cervix that is caused by strong uterine contractions. Pressure exerted by the amniotic fluid while the membranes are intact or by the force applied by the presenting part also can promote cervical dilation. Scarring of the cervix as a result of prior infection or surgery may slow cervical dilation.
In the first and second stages of labor, increased intrauterine pressure caused by contractions exerts pressure on the descending fetus and the cervix. When the presenting part of the fetus reaches the perineal floor, mechanical stretching of the cervix occurs. Stretch receptors in the posterior vagina cause release of endogenous oxytocin that triggers the maternal urge to bear down, or the Ferguson reflex.
Uterine contractions are usually independent from external forces. For example, laboring women who are paraplegic will have normal but painless uterine contractions (Cunningham et al., 2001). Uterine contractions may decrease temporarily in frequency and intensity if narcotic analgesic medication or epidural analgesia is given early in labor (Alexander et al., 1998). The exact relationship between prolonged labor and epidural analgesia continues to be investigated (Thompson et al., 1998).
As soon as the presenting part reaches the pelvic floor the contractions change in character and become expulsive. The laboring woman experiences an involuntary urge to push. She uses secondary powers (bearing-down efforts) to aid in expulsion of the fetus as she contracts her diaphragm and abdominal muscles and pushes. These bearing-down efforts result in increased intraabdominal pressure that compresses the uterus on all sides and adds to the power of the expulsive forces.
The secondary powers have no effect on cervical dilation, but they are of considerable importance in the expulsion of the infant from the uterus and vagina after the cervix is fully dilated. Studies have shown that pushing in the second stage is more effective and the woman is less fatigued when she begins to push only after she has the urge to do so rather than beginning to push when she is fully dilated without an urge to do so (Roberts & Woolley, 1996).
When and how a woman pushes in second stage is a much-debated topic. Studies have investigated the effects of spontaneous bearing-down efforts, directed pushing, delayed pushing, Valsalva (closed glottis and prolonged bearing down) pushing, and open glottis pushing (Peterson & Besuner, 1997; Roberts & Woolley, 1996; Sampselle, 1999; Thomson, 1995). Although no significant differences have been found in the duration of second-stage labor, adverse consequences have been reported. Fetal hypoxia and subsequent acidosis have been associated with prolonged breath holding and forceful pushing efforts (Mayberry et al., 1999). Perineal tears have been associated with directed pushing. Continued study is needed to determine the effectiveness and appropriateness of teaching strategies used by nurses to teach pushing techniques, the suitability and effectiveness of various pushing techniques related to nonreassuring fetal heart patterns, and the standards for length of pushing in terms of maternal and fetal outcomes (Minato, 2000/2001).
POSITION OF THE LABORING WOMAN
Fig. 12 Positions for labor and birth. A, Positions for labor. B, Positions for giving birth.
Position affects the woman's anatomic and physiologic adaptations to labor. Frequent changes in position relieve fatigue, increase comfort, and improve circulation. Therefore a laboring woman should be encouraged to find positions that are most comfortable to her (Fig. 12, A) (see Research box).
RESEARCH Position During Second Stage Labor
Western women usually give birth in the supine or lithotomy position, which is convenient for the clinician monitoring labor. In societies where squatting is customary for rest and defecation, squatting for second-stage labor is far more common. Researchers have claimed several advantages of upright position during delivery: gravity assistance, stronger and more effective uterine contractions, lessened aorta compression and less fetal acidosis, improved fetal alignment for birth, and increased pelvic outlet diameter. Upright positions include sitting (using obstetric chair or stool), semirecumbent, kneeling, squatting (unaided or using squatting bars), or squatting (using birth cushion).
A meta-analysis of 18 randomized and quasi-randomized trials compared labor outcomes of various positions used during second-stage labor. When compared with supine positions, upright position reduced second-stage labor by a mean of 5.4 minutes. This was greatly influenced by the rather large reduction (16.9 minutes) in the two trials of the birth cushion. The birth cushion trials also influenced the reduction in assisted deliveries with upright position, compared with supine positions. Women also had a decreased episiotomy rate when they delivered upright. Researchers speculated that the increased blood loss noted in upright labor may have been influenced by the fact that the birth chair has a receptacle for lost blood, so blood loss is measured. The researchers conclude that bearing down in the second stage of labor is more efficient in the upright position.They caution that poor overall study qualities preclude definite conclusions.
IMPLICATIONS FOR PRACTICE
Upright positions during second-stage labor may have advantages over supine positions, including prevention of cesarean birth because of failure to progress. Labor nurses should be familiar with different positions for second-stage labor so that they can help women find a position that feels right to them and also causes labor to progress. Although upright positions can be maintained without special equipment, availability of birthing beds with squatting bars, birthing stools/chairs, and birthing balls would encourage birthing in a different position.
Source: Gupta, J., & Nikodem, V. (2001). Woman's position during second stage of labor (Cochrane Review). The Cochrane Library, Issue 2. Oxford: Update Software.
An upright position (walking, sitting, kneeling, or squatting) offers a number of advantages. Gravity can promote the descent of the fetus. Uterine contractions are generally stronger and more efficient in effacing and dilating the cervix, resulting in shorter labor (Shermer & Raines, 1997; Simkin & Ancheta, 2000).
An upright position is also beneficial to the mother's cardiac output, which normally increases during labor as uterine contractions return blood to the vascular bed. The increased cardiac output improves blood flow to the uteroplacental unit and the maternal kidneys. Cardiac output is compromised if the descending aorta and ascending vena cava are compressed during labor. Compression of these major vessels may result in supine hypotension that decreases placental perfusion. With the woman in an upright position, pressure on the maternal vessels is reduced and compression is prevented. If the woman wishes to lie down, a lateral position is suggested (Cunningham et al., 2001).
The "all fours" position (hands and knees) may be used to relieve backache if the fetus is in an occipitoposterior position and may assist in anterior rotation of the fetus and in cases of shoulder dystocia (Simkin 1995; Simkin & Ancheta, 2000).
Positioning for second-stage labor (Fig. 12, B) may be determined by the woman's preference, but it is constrained by the condition of the woman or fetus, the environment, and the health care provider's confidence in assisting in a birth in a specific position (Simkin & Ancheta, 2000). The predominant position in the United States in physician-attended births is the lithotomy position. Alternative positions and position changes are more commonly practiced by nurse-midwives (Hanson, 1998).
A woman who pushes in a semirecumbent position needs adequate body support to push effectively because her weight will be on her sacrum, moving the coccyx forward and causing a reduction in the pelvic outlet. In a sitting or squatting position, abdominal muscles work in greater synchronicity with uterine contractions during bearing-down efforts. Kneeling or squatting moves the uterus forward and aligns the fetus with the pelvic inlet and can facilitate the second stage of labor by increasing the pelvic outlet (Simkin & Ancheta, 2000).
The lateral position can be used by the woman to help rotate a fetus that is in a posterior position. It can also be used when there is a need for less force to be used during bearing down such as when there is a need to control the speed of a precipitous birth (Roberts & Woolley, 1996; Simkin & Ancheta, 2000).
There is no evidence that any of these positions suggested for second-stage labor increase the need for use of operative techniques (e.g., forceps- or vacuum-assisted birth, cesarean birth, episiotomy) or cause perineal trauma. There is also no evidence that use of any of these positions adversely affects the newborn (Mayberry et al., 2000).
PROCESS OF LABOR
Labor is the process of moving the fetus, placenta, and membranes out of the uterus and through the birth canal. Various changes take place in the woman's reproductive system in the days and weeks before labor begins. Labor itself can be discussed in terms of the mechanisms involved in the process and the stages the woman moves through.
SIGNS PRECEDING LABOR
In first-time pregnancies the uterus sinks downward and forward approximately 2 weeks before term, when the fetus's presenting part (usually the fetal head) descends into the true pelvis. This settling is called lightening, or "dropping," and usually happens gradually. After lightening, women feel less congested and breathe more easily. However, there is usually more bladder pressure as a result of this shift and consequently a return of urinary frequency. In a multiparous pregnancy, lightening may not take place until after uterine contractions are established and true labor is in progress.
The woman may complain of persistent low backache and sacroiliac distress as a result of relaxation of the pelvic joints. She may identify strong, frequent, but irregular uterine (Braxton Hicks) contractions.
The vaginal mucus becomes more profuse in response to the extreme congestion of the vaginal mucous membranes. Brownish or blood-tinged cervical mucus may be passed (bloody show). The cervix becomes soft (ripens) and partially effaced and may begin to dilate. The membranes may rupture spontaneously.
Other phenomena are common in the days preceding labor: (1) loss of 0.5 to 1.5 kg in weight, caused by water loss resulting from electrolyte shifts that in turn are produced by changes in estrogen and progesterone levels; and (2) a surge of energy. Women speak of having a burst of energy that they often use to clean the house and put everything in order. Less commonly, some women experience diarrhea, nausea, vomiting, and indigestion (Varney, 1997). Box 1 lists signs that may precede labor.
Box 1 Signs Preceding Labor
Return of urinary frequency
Stronger Braxton Hicks contractions
Weight loss 0.5-1.5 kg
Surge of energy
Increased vaginal discharge; bloody show
Membranes may rupture
ONSET OF LABOR
The onset of true labor cannot be ascribed to a single cause. Many factors, including changes in the maternal uterus, cervix, and pituitary gland, are involved. Hormones produced by the normal fetal hypothalamus, pituitary, and adrenal cortex probably contribute to the onset of labor. Progressive uterine distention, increasing intrauterine pressure, and aging of the placenta seem to be associated with increasing myometrial irritability. This is a result of increased concentrations of estrogen and prostaglandins, as well as decreasing progesterone levels. The mutually coordinated effects of these factors result in the occurrence of strong, regular, rhythmic uterine contractions. Normally, the outcome of these factors working together is the birth of the fetus and the expulsion of the placenta. However, it is still not completely understood how certain alterations trigger others and how proper checks and balances are maintained.
Fetal fibronectin is a protein found in plasma and cervicovaginal secretions of pregnant women before the onset of labor. Assessment for the presence of fetal fibronectin is being used to predict the likelihood of preterm labor in women who are at increased risk for this complication. The value of detection of fetal fibronectin in management of women with preterm labor has yet to be determined (Coleman et al., 1998; Goldenberg et al, 2000).
STAGES OF LABOR
Labor is considered "normal" when the woman is at or near term, no complications exist, a single fetus presents by vertex, and labor is completed within 24 hours. The course of normal labor, which is remarkably constant, consists of (1) regular progression of uterine contractions, (2) effacement and progressive dilation of the cervix, and (3) progress in descent of the presenting part. Four stages of labor are recognized. These stages are discussed in greater detail, along with nursing care for the laboring woman and family.
The first stage of labor is considered to last from the onset of regular uterine contractions to full dilation of the cervix. The onset of labor is often difficult to establish because the woman may be admitted to the labor unit just before birth and the beginning of labor may be only an estimate. The first stage is much longer than the second and third combined. Great variability is the rule, however, depending on the factors discussed previously in this chapter. Full dilation may occur in less than 1 hour in some multiparous pregnancies. In first-time pregnancy, complete dilation of the cervix can take up to 20 hours. There are no absolute values for the normal length of the first stage of labor (American College of Obstetricians and Gynecologists [ACOG], 1995). Variations may reflect differences in the patient population or in clinical practice.
The first stage of labor has been divided into three phases: a latent phase, an active phase, and a transition phase. During the latent phase there is more progress in effacement of the cervix and little increase in descent. During the active phase and the transition phase there is more rapid dilation of the cervix and increased rate of descent of the presenting part.
The second stage of labor lasts from the time the cervix is fully dilated to the birth of the fetus. The second stage takes an average of 20 minutes for a multiparous woman and 50 minutes for a nulliparous woman. Labor of up to 2 hours has been considered within the normal range for the second stage, but there can be significant variations. For example, a woman who has received epidural analgesia may take up to 3 hours (Johnson & Rosenfeld, 1995). As long as there is progress and the fetal status is reassuring, the length of the second stage is usually not related to adverse perinatal outcomes (ACOG, 1995).
Simkin and Ancheta (2000) describe the latent and active phases of second-stage labor. The latent phase is a period that begins around the time of complete dilation of the uterus when the contractions are weak or not noticeable and the woman is not feeling the urge to push, is resting, or is exerting only small bearing-down efforts with contractions. The active phase is a period when contractions resume and the woman is making strong bearingdown efforts and the fetal station is advancing.
The third stage of labor lasts from the birth of the fetus until the placenta is delivered. The placenta normally separates with the third or fourth strong uterine contraction after the infant has been born. After it has separated, the placenta can be delivered with the next uterine contraction. The duration of the third stage may be as short as 3 to 5 minutes, although up to 1 hour is considered within normal limits. The risk of hemorrhage increases as the length of the third stage increases (Cunningham et al, 2001).
The fourth stage of labor arbitrarily lasts approximately 2 hours after delivery of the placenta. It is the period of immediate recovery, when homeostasis is reestablished. It serves as an important period of observation for complications, such as abnormal bleeding.
MECHANISM OF LABOR
Fig. 13 Cardinal movements of the mechanism of labor. Left occipitoanterior (LOA) presentation. A, Engagement and descent. B, Flexion. C, Internal rotation to occipitoanterior position (OA). D, Extension. E, External rotation beginning (restitution). F, External rotation.
As already discussed, the female pelvis has varied contours and diameters at different levels, and the presenting part of the passenger is large in proportion to the passage. Therefore, for vaginal birth to occur, the fetus must adapt to the birth canal during the descent. The turns and other adjustments necessary in the human birth process are termed the mechanism of labor (Fig. 13). The seven cardinal movements of the mechanism of labor that occur in a vertex presentation are engagement, descent, flexion, internal rotation, extension, external rotation (restitution), and finally birth by expulsion. Although these movements are discussed separately, in actuality a combination of movements occurs simultaneously. For example, engagement involves both descent and flexion.
When the biparietal diameter of the head passes the pelvic inlet, the head is said to be engaged in the pelvic inlet (see Fig. 13, A). In most nulliparous pregnancies this occurs before the onset of active labor because the firmer abdominal muscles direct the presenting part into the pelvis. In multiparous pregnancies, in which the abdominal musculature is more relaxed, the head often remains freely movable above the pelvic brim until labor is established.
Asynclitism. The head usually engages in the pelvis in a synclitic position, one that is parallel to the anteroposterior plane of the pelvis. Frequently asynclitism occurs (the head is deflected anteriorly or posteriorly in the pelvis), which can facilitate descent because the head is being positioned to accommodate to the pelvic cavity (Fig. 14). However, extreme asynclitism can cause cephalopelvic disproportion, even in a normal-size pelvis, because the head is positioned so that it cannot descend.
Fig. 14 Synclitism and asynclitism. A, Anterior asynclitism. B, Normal synclitism. C, Posterior asynclitism.
Descent refers to the progress of the presenting part through the pelvis. Descent depends on at least four forces: (1) pressure exerted by the amniotic fluid, (2) direct pressure exerted by the contracting fundus on the fetus, (3) force of the contraction of the maternal diaphragm and abdominal muscles in the second stage of labor, and (4) extension and straightening of the fetal body. The effects of these forces are modified by the size and shape of the maternal pelvic planes and the size of the fetal head and its capacity to mold.
The degree of descent is measured by the station of the presenting part (see Fig. 6). As mentioned, little descent occurs during the latent phase of the first stage of labor. Descent accelerates in the active phase when the cervix has dilated to 5 to 7 cm. It is especially apparent when the membranes have ruptured.
In a first-time pregnancy descent is usually slow but steady; in subsequent pregnancies descent may be rapid. Progress in descent of the presenting part is determined by abdominal palpation (Leopold's maneuvers) and vaginal examination until the presenting part can be seen at the introitus.
As soon as the descending head meets resistance from the cervix, pelvic wall, or pelvic floor, it normally flexes so that the chin is brought into closer contact with the fetal chest (see Fig. 13, B). Flexion permits the smaller suboccipitobregmatic diameter (9.5 cm) rather than the larger diameters to present to the outlet.
The maternal pelvic inlet is widest in the transverse diameter. Therefore the fetal head passes the inlet into the true pelvis in the occipitotransverse position. The outlet is widest in the anteroposterior diameter, however. Therefore, for the fetus to exit, the head must rotate. Internal rotation begins at the level of the ischial spines but is not completed until the presenting part reaches the lower pelvis. As the occiput rotates anteriorly, the face rotates posteriorly. With each contraction the fetal head is guided by the bony pelvis and the muscles of the pelvic floor. Eventually, the occiput will be in the midline beneath the pubic arch. The head is almost always rotated by the time it reaches the pelvic floor (see Fig. 13, Q. Both the levator ani muscles and the bony pelvis are important for achieving anterior rotation. A previous childbirth injury or regional anesthesia may compromise the function of the levator sling.
When the fetal head reaches the perineum for birth, it is deflected anteriorly by the perineum. The occiput passes under the lower border of the symphysis pubis first, then the head emerges by extension: first the occiput, then the face, and finally the chin (see Fig. 13, D).
Restitution and external rotation
After the head is born, it rotates briefly to the position it occupied when it was engaged in the inlet. This movement is termed restitution (see Fig. 13, E). The 45-degree turn realigns the infant's head with her or his back and shoulders. The head can then be seen to rotate further. This external rotation occurs as the shoulders engage and descend in maneuvers similar to those of the head (see Fig. 13, F). As noted earlier, the anterior shoulder descends first. When it reaches the outlet, it rotates to the midline and is delivered from under the pubic arch. The posterior shoulder is guided over the perineum until it is free of the vaginal introitus.
After birth of the shoulders, the head and shoulders are lifted up toward the mother's pubic bone and the trunk of the baby is born by flexing it laterally in the direction of the symphysis pubis. When the baby has completely emerged, birth is complete, and the second stage of labor ends.
PREPARATION FOR DELIVERY.
Delivery can be accomplished with the mother in a variety of positions. The most widely used and often the most satisfactory one is the dorsal lithotomy position in order to increase the diameter of the pelvic outlet. In many birthing rooms this is accomplished with the woman lying flat on the bed. For better exposure, leg holders or stirrups are used. In placing the legs in leg holders, care should be taken not to separate the legs too widely or place one leg higher than the other, as this will exert pulling forces on the perineum that might easily result in the extension of a spontaneous tear or an episiotomy into a fourth-degree tear. The popliteal region should rest comfortably in the proximal portion and the heel in the distal portion of the leg-holder. The leg should not be forced to conform to the preexisting setting. The legs are not strapped into the stirrups, thereby allowing quick flexion of the thighs back onto the abdomen should shoulder dystocia be encountered. Cramps in the legs may develop during the second stage in part because of pressure by the fetal head on nerves in the pelvis. Such cramps may be relieved by changing the position of the leg or by brief massage, but leg cramps should never be ignored.
Preparation for delivery entails vulvar and perineal cleansing. If desired, sterile drapes may be placed in such a way that only the immediate area about the vulva is exposed (Fig. 13-3). In the past, the major reason for care in scrubbing, gowning, and gloving was to protect the laboring woman from the introduction of infectious agents. Although these considerations remain valid, concern today also must be extended to the health-care providers, because of the threat of exposure to human immunodeficiency virus. Recommendations for protection of those who care for women during labor and delivery are summarized in Chapter 57 (p. 1498).
DELIVERY OF THE HEAD
With each contraction, the perineum bulges increasingly and the vulvovaginal opening becomes more dilated by the fetal head ), gradually forming an ovoid and finally an almost circular opening. With the cessation of each contraction, the opening becomes smaller as the head recedes. As the head becomes increasingly visible, the vaginal outlet and vulva are stretched further until they ultimately encircle the largest diameter of the fetal head (Fig. 13-5). This encirclement of the largest head diameter by the vulvar ring is known as crowning.
Unless an episiotomy has been made, as described later in the chapter, the perineum by now is extremely thin and, especially in the case of the nulliparous woman, may undergo spontaneous laceration. At the same time, the anus becomes greatly stretched and protuberant, and the anterior wall of the rectum may be easily seen through it. Over many years there has been considerable controversy concerning whether an episiotomy should be cut. We advocate individualization and do not routinely cut an episiotomy. It is now clear that an episiotomy will increase the risk of a tear into the external anal sphincter and/or the rectum. Conversely, anterior tears involving the urethra and labia are much more common in women in whom an episiotomy is not cut.
Immediately after delivery of the infant, there is usually a gush of amnionic fluid, often tinged with blood but not grossly bloody.
CLEARING THE NASOPHARYNX. To minimize the likelihood of aspiration of amnionic fluid, debris, and blood that might occur once the thorax is delivered and the infant can inspire, the face is quickly wiped and the nares and mouth are aspirated.
NUCHAL CORD. Following delivery of the anterior shoulder, the finger should be passed to the neck of the fetus to ascertain whether it is encircled by one or more coils of the umbilical cord (Fig. 13-11). Nuchal cords occur in about 25 percent of cases and ordinarily do no harm. If a coil of umbilical cord is felt, it should be drawn down between the fingers and, if loose enough, slipped over the infant's head. If it is applied too tightly to the neck to be slipped over the head, it should be cut between two clamps and the infant promptly delivered.
CLAMPING THE CORD
The umbilical cord is cut between two clamps placed 4 or 5 cm from the fetal abdomen, and later an umbilical cord clamp is applied 2 or 3 cm from the fetal abdomen. A plastic clamp (Hollister, Double Grip Umbilical Clamp) that is safe, efficient, easy to sterilize, and fairly inexpensive is shown in Figure 13-12.
TIMING OF CORD CLAMPING.
If, after delivery, the infant is placed at or below the level of the vaginal introitus for 3 minutes and the fetoplacental circulation is not immediately occluded by clamping the cord, an average of 80 mL of blood may be shifted from the placenta to the infant (Yao and Lind, 1974). One benefit to be derived from placental transfusion is that the hemoglobin in 80 mL of placental blood that shifts to the fetus eventually provides about 50 mg of iron, which reduces the frequency of iron-deficiency anemia later in infancy. In the presence of accelerated destruction of erythrocytes, as occurs with maternal alloimmunization, the bilirubin formed from the added erythrocytes contributes further to the danger of hyperbilirubinemia (Chap. 39, p. 1061). Although the theoretical risk of circulatory overloading from gross hypervolemia is formidable, especially in preterm and growth-retarded infants, addition of placental blood to the otherwise normal infant's circulation ordinarily does not cause difficulty.
Our policy is to clamp the cord after first thoroughly clearing the airway, all of which usually takes about 30 seconds. The infant is not elevated above the introitus at vaginal delivery or much above the maternal abdominal wall at the time of cesarean delivery.
MANAGEMENT OF THE THIRD STAGE
Immediately after delivery of the infant, the height of the uterine fundus and its consistency are ascertained. As long as the uterus remains firm and there is no unusual bleeding, watchful waiting until the placenta is separated is the usual practice. No massage is practiced; the hand is simply rested on the fundus frequently, to make certain that the organ does not become atonic and filled with blood behind a separated placenta.
SIGNS OF PLACENTAL SEPARATION
Because attempts to express the placenta prior to its separation are futile and possibly dangerous, it is most important that the following signs of placental separation be recognized:
1. The uterus becomes globular and, as a rule, firmer. This sign is the earliest to appear.
2. There is often a sudden gush of blood.
3. The uterus rises in the abdomen because the placenta, having separated, passes down into the lower uterine segment and vagina, where its bulk pushes the uterus upward.
4. The umbilical cord protrudes farther out of the vagina, indicating that the placenta has descended.
These signs sometimes appear within about 1 minute after delivery of the infant and usually within 5 minutes. When the placenta has separated, it should be ascertained that the uterus is firmly contracted. The mother may be asked to bear down, and the intra-abdominal pressure so produced may be adequate to expel the placenta. If these efforts fail, or if spontaneous expulsion is not possible because of anesthesia, and after ensuring that the uterus is contracted firmly, pressure is exerted with the hand on the fundus to propel the detached placenta into the vagina, as depicted and described in Figure 13-13. This approach has been termed physiological management, as later to be contrasted with "active management" of the third stage (Thilaganathan and colleagues, 1993).
DELIVERY OF THE PLACENTA
Placental expression should never be forced before placental separation lest the uterus be turned inside out. Traction on the umbilical cord must not be used to pull the placenta out of the uterus. Inversion of the uterus is one of the grave complications associated with delivery (Chap. 25, p. 642). As pressure is applied to the body of the uterus (Fig. 13-13), the umbilical cord is kept slightly taut. The uterus is lifted cephalad with the abdominal hand. This maneuver is repeated until the placenta reaches the introitus (Prendiville and associates, 1988b). As the placenta passes through the introitus, pressure on the uterus is stopped. The placenta is then gently lifted away from the introitus (Fig. 13-14). Care is taken to prevent the membranes from being torn off and left behind. If the membranes start to tear, they are grasped with a clamp and removed by gentle traction (Fig. 13-15). The maternal surface of the placenta should be examined carefully to ensure that no placental fragments are left in the uterus.
MANUAL REMOVAL OF PLACENTA.
Occasionally, the placenta will not separate promptly. This is especially common in cases of preterm delivery (Dombrowski and colleagues, 1995).. It is unclear as to the length of time that should elapse in the absence of bleeding before the placenta is manually removed. Manual removal of the placenta is rightfully practiced much sooner and more often than in the past. In fact, some obstetricians practice routine manual removal of any placenta that has not separated spontaneously by the time they have completed delivery of the infant and care of the cord in women with conduction analgesia. Proof of the benefits of this practice, however, has not been established, and most obstetricians await spontaneous placental separation unless bleeding is excessive.
ACTIVE MANAGEMENT OF THE THIRD STAGE
Thilaganathan and associates (1993) compared a regimen of active management with syntometrine (5 units of oxytocin with 0.5 mg of ergometrine) and controlled cord traction with one of physiological management wherein the cord was not clamped and the placenta was delivered by maternal efforts. Among 103 low-risk term deliveries, active management resulted in a reduction in the length of the third stage of labor, but no reduction in blood loss compared with physiological management. Mitchell and Elbourne (1993) found that syntometrine administered intramuscularly concurrent with delivery of the anterior shoulder was more effective than oxytocin (5 units intramuscularly) alone in the prevention of postpartum hemorrhage. Duration of the third stage of labor and need for manual removal of the placenta were similar. Side effects of nausea, vomiting, and blood pressure elevations with ergometrine prevented any recommendation for its routine usage.
PRETERM LABOR AND BIRTH
Preterm labor is defined as cervical changes and uterine contractions occurring between 20 and 37 weeks of pregnancy. Preterm birth is any birth that occurs before the completion of 37 weeks of pregnancy (American College of Obstetricians and Gynecologists & American Academy of Pediatrics, 1997). Preterm labor and birth are the most serious complications of pregnancy because they lead to approximately 90% of all neonatal deaths, with more than 75% of these deaths occurring in infants born at fewer than 32 weeks of gestation. Despite decreasing infant mortality rates in the United States, preterm birthrates have continued to rise. Preterm birth is the second leading cause of infant death. In 1999 the preterm birthrate for all races in the United States was 11.8%, having steadily risen from 9.4% in 1981 (March of Dimes, 1997; Ventura et al., 2001).
PRETERM BIRTH VERSUS LOW BIRTH WEIGHT
Although they have distinctly different meanings, the terms preterm birth and low birth weight are often used interchangeably. Preterm birth describes length of gestation (i.e., less than 37 weeks), whereas low birth weight describes only weight at the time of birth (i.e., 2500 g or less). Low birth weight is far easier to measure than preterm birth, and thus in many settings and publications, low birth weight has been used as a substitute term for preterm birth. Preterm birth, however, is a more dangerous health condition for an infant because length of time in the uterus correlates with immaturity of body systems. Low-birth-weight babies can be, but are not necessarily, preterm; low birth weight can be caused by conditions other than preterm birth, such as intrauterine growth restriction (IUGR), a condition of fetal undergrowth not necessarily correlated with initiation of labor.
The incidence of preterm birth in the United States varies according to race. The 1999 rate for African-Americans was 17.5%, whereas the rate for Hispanics was 11.4% and for Caucasians was 10.7%. Anecdotal evidence suggests that sociodemographics may play a part in this difference among races. Preterm birthrates are higher among socially disadvantaged populations, including minorities, women with low levels of education, and women who receive late or no prenatal care (Ventura et al., 2001).
PREDICTING PRETERM LABOR AND BIRTH
The known risk factors for preterm birth are shown in Box 1. Using these risk factors, researchers have tried to determine which women might go into labor prematurely. Risk assessment schema were developed and risk scoring systems were used (Collaborative Group on Preterm Birth Prevention, 1993). None of these risk scoring systems has resulted in lowering the preterm birthrate in the United States, however, because at least 50% of all women who ultimately give birth prematurely have no identifiable risk factors. Programs aimed at decreasing preterm birthrates must include women labeled as "high risk for preterm birth" and women with no identifiable risk factors. Unless all women are included in prevention efforts that begin in the first trimester, a widespread reduction of preterm birthrates cannot be expected (Maloni, 2000).
BOX 1 Risk Factors for Preterm Labor
• Nonwhite race
• Age (<17, >35)
• Low socioeconomic status
• Less than high school education
• Previous preterm labor or birth
• Second-trimester abortion (more than two spontaneous or therapeutic); still births
• Grand multiparity; short interval between pregnancies <1 year since last birth); family history of preterm labor and birth
• Progesterone deficiency
• Uterine anomalies or fibroids; uterine irritability
• Cervical incompetence, trauma, shortened length
• Exposure to DES or other toxic substances
• Medical diseases (e.g., diabetes, hypertension, anemia)
• Small stature (< 119 cm in height; <45.5 kg or underweight for height)
• Current pregnancy risks:
• Multifetal pregnancy
• Placental problems (e.g., placenta previa, abruption placentae)
• Infections (e.g., pyelonephritis, recurrent urinary tract infections, asymptomatic bacteriuria, bacterial vaginosis, chorioamnionitis)
• Pregnancy-induced hypertension
• Premature rupture of the membranes
• Fetal anomalies
• Inadequate plasma volume expansion; anemia
• Poor nutrition; weight loss or low weight gain
• Smoking (>10 cigarettes a day)
• Substance abuse (e.g., alcohol; illicit drugs, especially cocaine)
• Inadequate prenatal care
• Commutes of more than 1V2 hours each way
• Excessive physical activity (heavy physical work, prolonged standing, heavy lifting, young child care)
• Excessive lifestyle stressors
The two most common biochemical markers used in an effort to predict who might experience preterm labor are fetal fibronectin and salivary estriol. Fetal fibronectins are glycoproteins found in plasma and produced during fetal life. They appear in the cervical canal early in pregnancy, and then again in late pregnancy. Their appearance between 24 and 34 weeks of gestation could predict preterm labor. The negative predictive value of fetal fibronectins is high (up to 95%). The positive predictive value of the fetal fibronectin test is lower (25% to 40%) (Moore, 1999). This means that it may be possible to predict who will not go into preterm labor, but not who will. The test is done during a vaginal examination.
Salivary estriol is a form of estrogen produced by the fetus that is present in plasma at 9 weeks of gestation. Levels of salivary estriol have been shown to increase before preterm birth. Specimens of salivary estriol are collected by the woman in the home; the testing is done every 2 weeks for approximately 10 weeks. This marker also has a high negative predictive value (98%) and a lower positive predictive value (7% to 25%) (Moore, 1999).
Some studies have suggested that a shortened cervix precedes preterm labor and can be determined by ultrasound measurement (Crane et al., 1997). A shortened cervical length of less than 30 mm in a singleton pregnancy can predict some instances of preterm labor. When a woman has a short cervix combined with a positive fetal fibronectin result, her risk for spontaneous preterm birth is substantially higher than for women positive for only one marker or none at all (Goldenberg et al., 2000).
Causes of preterm labor and birth
The cause of preterm labor is unknown and is assumed to be multifactorial (Goldenberg & Rouse, 1998; Maloni, 2000) (Box 2). Infection is thought to be a major etiologic factor in some preterm labors. When cervical, vaginal, or urinary tract infections are present, the risk of preterm birth is increased (Box 3). Thus early, continuous, and comprehensive prenatal care, which can detect and treat infection, is essential in dealing with this aspect of preterm birth prevention.
BOX 2 Multifactorial Etiology of Preterm Labor and Birth
Substance use (alcohol or illegal drugs)
Short interpregnancy interval
Young or old age
Previous preterm birth
Prematurely dilated cervix
Low prepregnancy weight
Low socioeconomic status
Victim of domestic violence
Inadequate support systems
Late or no prenatal care
Preterm premature rupture of membranes
Decreased progesterone production
Decidual cell disruption
BOX 3 Infections and Risk of Preterm Labor
Bacterial vaginosis 40% increased risk
Syphilis and gonorrhea 50% increased risk
Asymptomatic bacteriuria 50% increased risk
Not all preterm births can or even should be prevented. Approximately 25% of all preterm births are iatrogenic; that is, babies are intentionally delivered prematurely be cause of pregnancy complications that put the life or health of the fetus or mother in danger, not because of preterm labor. Another 25% of all preterm births are preceded by spontaneous rupture of the membranes followed by labor. These preterm births are not known to be preventable. Approximately 50% of preterm births, therefore, are possibly amenable to prevention efforts and are considered idiopathic preterm births (Goldenberg & Rouse, 1998).
Sociodemographic factors such as poverty, low educational level, lack of social support, smoking, little or no prenatal care, domestic violence, and stress are thought to contribute to the 50% of preterm births that may be preventable (Curry, Perrm, & Wall, 1998; McFarlane & Gondolf, 1998; Moore & Freda, 1998). If prenatal care programs are to be effective in reducing the rate of preterm labor and birth, they must address these sociodemographic factors and develop strategies to attract all women to participate, including those at high risk for preterm labor (Maloni, 2000). Addressing the factors that contribute to preterm labor and birth can produce significant results. For example, Janke (1999) found that when women at risk for preterm birth participated in a daily program of relaxation to reduce stress and anxiety, they experienced prolonged pregnancies and gave birth to larger newborns with significantly longer gestations.
Assessment and Nursing Diagnoses
Because all pregnant women must be considered at risk for preterm labor (as they are for any other pregnancy complication), nursing assessment begins at the time of entry to prenatal care. Because the onset of preterm labor is often insidious and can be easily mistaken for normal discomforts of pregnancy, it is essential that nurses teach pregnant women how to detect the early symptoms of preterm labor (Box 24-4) (Freston et al., 1997; Peck & Griffis, 1999).
Pregnant women need to be taught what to do if the symptoms of preterm labor occur. Some women wait hours or days before contacting a health care provider after preterm labor symptoms have begun (Freston et al., 1997). Waiting too long to see a health care provider could result in inevitable preterm birth without the benefit of the administration of antenatal glucocorticoids. In this event the neonate is born at higher risk for respiratory distress syndrome and intraventricular hemorrhage. Nursing diagnoses relevant for women at risk for preterm birth include the following:
• Deficient knowledge related to
-recognition of preterm labor symptoms
• Risk for maternal or fetal injury related to
-preterm labor and birth
• Impaired mobility related to
-prescribed bed rest
• Anticipatory grieving related to
-preterm labor and birth
Expected Outcomes of Care
Expected outcomes include that the woman will do the following:
• Learn the symptoms of preterm labor and be able to assess herself and her need for intervention
• Follow teaching suggestions and call her physician or nurse-midwife if symptoms occur
• Not experience preterm symptoms, or if she does, she will take appropriate action
• Maintain her pregnancy for at least 37 completed weeks
• Give birth to a healthy, term infant
Plan of Care and Interventions
Prevention strategies that address risk factors associated with preterm labor and birth are less costly in human and financial terms than the high-tech and often lifelong care required by preterm infants and their families. Programs aimed at health promotion and disease prevention that encourage healthy lifestyles for the population in general and women of childbearing age in particular should be developed in an effort to prevent preterm labor and birth (Heaman, Sprague, & Stewart, 2001). One of the most important nursing interventions aimed at preventing preterm birth is the education of pregnant women about the early symptoms of preterm labor, so that if the symptoms occur the woman can be referred promptly to her physician or nurse-midwife for more intensive care. Box 4 identifies the symptoms of preterm labor, and the Guidelines/Guias box identifies what the woman should do if the symptoms appear. Patient education regarding any symptoms of uterine contractions or cramping between 20 and 37 weeks of gestation should be directed toward telling the woman that these symptoms are not normal discomforts of pregnancy and that contractions or cramping that do not go away should prompt the woman to contact her physician or nurse-midwife. Because no one can discriminate between Braxton-Hicks contractions and the contractions of early preterm labor, Freda and Patterson (1995) suggest that the term Braxton-Hicks contractions be eliminated from teaching about pregnancy expectations (Fig. 1).
BOX 4 Signs and Symptoms of Preterm Labor
• Uterine contractions more frequent than every
10 minutes persisting for 1 hour or more
• Uterine contractions may be painful or painless
• Lower abdominal cramping similar to gas pains; may be accompanied by diarrhea
• Dull, intermittent low back pain (below the waist)
• Painful, menstrual-like cramps
• Suprapubic pain or pressure
• Pelvic pressure or heaviness
• Urinary frequency
• Change in character and amount of usual discharge: thicker (mucoid) or thinner (watery), bloody, brown or colorless, increased amount, odor
• Rupture of amniotic membranes
Fig, 1 Nurse teaching woman signs and symptoms of preterm labor. (Courtesy Marjorie Pyle, RNC, Lifecircle, Costa Mesa, CA.)
Early recognition and diagnosis
Early recognition of preterm labor is essential to successfully implement interventions such as tocolytic therapy and administration of antenatal glucocorticoids. According to the American College of Obstetricians and Gynecologists and American Academy of Pediatrics (1997), the diagnostic criteria for preterm labor are 20 to 37 weeks of gestation; documented uterine contractions; and either documented cervical change, cervical effacement of 80%, or cervical dilation of greater than 1 cm. Therefore the pregnant woman at 30 weeks with an irritable uterus but no documented cervical change is not in preterm labor. Misdiagnosis of preterm labor can lead to inappropriate use of pharmacologic agents that can be dangerous to the health of the woman or fetus.
Nurses caring for women who exhibit symptoms of preterm labor should question the woman about whether she has symptoms when engaged in any of the following activities:
• Sexual activity
• Riding long distances in automobiles, trains, or buses
• Carrying heavy loads such as laundry, groceries, or a small child
• Standing more than 50% of the time
• Heavy housework
• Climbing stairs
• Hard physical work
• Being unable to stop and rest when tired
If symptoms occur when the woman is engaged in any of these activities, the woman should consider what she was doing when the symptoms began, and then consider stopping those activities until 37 weeks of pregnancy when preterm birth is no longer a risk. Counseling about lifestyle modification should be individualized; only women who have symptoms of preterm labor when they are engaged in certain activities need to alter their lifestyles. There are no specific rules for which activities are safe for pregnant women and which are not. Each pregnant woman must understand which lifestyle factors might be contributing to her symptoms and be taught to modify only those factors. Sexual activity, for instance, is not prohibited during pregnancy. If, however, symptoms of preterm labor occur after sexual activity, that activity may need to be curtailed until 37 weeks of gestation.
Bed rest is a commonly used intervention for the prevention of preterm birth. There is no evidence in the literature to support the efficacy of this intervention, however. Maloni and colleagues (1993) have shown that there are deleterious effects of bed rest on women: after 3 days there is decreased muscle tone, weight loss, calcium loss, and glucose intolerance. Weeks of bed rest lead to bone demineralization, constipation, fatigue, isolation, anxiety, and depression (Box 5). May (1994) has also documented the father's sense of constant worry when bed rest is prescribed for his wife. Bed rest is costly for society; the estimated economic costs are based on lost wages, household and child care help expenses, and hospital costs (Goldenberg et al., 1994) (see Research box). Women on bed rest need support and encouragement whether they are at home or are hospitalized. Nurses can create support groups of hospitalized women on bed rest. Internet resources, as well as family and friends, can be important sources of support for the woman at home on bed rest (Maloni & Kuril, 2000).
BOX 5 Adverse Effects of Bed Rest
MATERNAL EFFECTS (PHYSICAL)
• Weight loss
• Muscle wasting, weakness
• Bone demineralization and calcium loss
• Decreased plasma volume and cardiac output
• Increased clotting tendency; risk for thrombophlebitis
• Alteration in bowel function
• Sleep disturbance, fatigue
• Prolonged postpartum recovery
MATERNAL EFFECTS (PSYCHOSOCIAL)
• Loss of control associated with role reversals
• Dysphoria—anxiety, depression, hostility, and anger
• Guilt associated with difficulty complying with activity restriction and inability to meet role responsibilities
• Boredom, loneliness
• Emotional lability (mood swings)
EFFECTS ON SUPPORT SYSTEM
• Stress associated with role reversals, increased responsibilities, and disruption of family routines
• Financial strain associated with loss of maternal income and cost of treatment
• Fear and anxiety regarding the well-being of the mother and fetus
Bed rest, although frequently prescribed, is not a benign intervention and has furthermore never been shown to decrease preterm birthrates (Maloni, 1998). Women who are at high risk for preterm birth commonly are told that it would be best if they were at home on bed rest for weeks or months. The home care of the woman at risk for preterm birth is a challenge for the nurse, who needs to assist the woman and her family in dealing with the many difficulties faced by families in which one member must be incapacitated. The scope of care given to women in their homes could range from occasional visits to monitor the maternal and fetal condition to daily telephone consultation and reading of uterine monitoring strips. Families, who are often anxious regarding the health status of the mother and baby, may need help in learning how to organize time and space or restructure family routines so that the pregnant woman can remain a part of family activity while still maintaining bed rest. It is also important for the nurse to work toward assisting all the family members to explore their feelings regarding the anxieties of preterm labor and help them to share their feelings with each other (Maloni, Brezinski-Tomasi, & Johnson, 2001) (Fig. 2 and Box 6) (see Self-Care box).
Fig. 2 Woman at home on restricted activity for preterm labor prevention. Note how she has arranged her daytime resting area so that needed items are close at hand. (Courtesy Amy Turner, Cary, NC.)
BOX 6 Activities for Children of Women on Bed Rest
• Schedule brief play periods throughout the day.
• Keep a few favorite toys in a box or basket close to the bed or couch.
• Read to the child(ren).
• Put puzzles together.
• Watch videos, play video games (remote control for TV is ideal).
• Play cards or board games.
• Color in coloring books.
• Cut out pictures from magazines and paste on cardboard.
• Play bed basketball with a soft (sponge) ball or rolled up sock and a trash can or empty laundry basket.
Patient Instructions for Self-Care
Suggested Activities for Women on Bed Rest
• Set a routine for daily activities (e.g., getting dressed, moving from the bedroom to a "day bed rest place," having social time, eating meals, self-monitoring fetal and uterine activity)
• Do passive exercises as allowed
• Review childbirth education information or have a childbirth class at home, if this can be arranged
• Plan menus and make up grocery shopping lists
• Shop by phone
• Read books about high risk pregnancy or other topics
• Keep a journal of the pregnancy
• Keep a calendar of your progress
• Reorganize files, recipes, household budget
• Update address book
• Do mending, sewing
• Listen to audiotapes, watch videos orTV
• Do crossword puzzles, jigsaw puzzles, etc.
• Do craft projects; make something for the baby
• Put pictures in photo albums
• Call a friend, family member, or support person each day or use email
• Treat yourself to a facial, manicure, neck massage, or other special treat when you need a lift
Horns uterine activity monitoring
Home care agencies provide home uterine monitoring services for women diagnosed with preterm labor (Fig. 3). However, from the body of research over the past 15 years, researchers have concluded that home uterine activity monitoring does not prevent preterm birth, and its prohibitive cost makes it an unacceptable intervention in the larger scheme of prenatal care (Dyson et al., 1998; Maloni, 2000). The use and effectiveness of home uterine activity monitoring remains controversial (Roberts & Morrison, 1998). Some research suggests that it is the nursing care offered by the home care nurse that helps women the most (lams, Johnson, & O'Shaughnessy, 1988; Moore et al., 1998).
Fig. 3 Home uterine activity monitoring. Tocodynamometer is in place at center of abdomen below umbilicus. Recording unit and transmitter are on bedside table. (Courtesy Michael S. Clement, MD, Mesa, AZ.)
Suppression of uterine activity
Tocolytics. Should preterm labor occur, women are usually admitted to the hospital for assessment; fetal monitoring; cervical/vaginal cultures; and assessment of cervical status, amniotic fluid leakage, and maternal temperature (an early sign of chorioamnionitis). The initiation of tocolytic therapy might be considered at this time. Tocolytics have been the subject of research since the late 1970s (Viamantes, 1996). At first, it was thought that use of tocolytic therapy could prolong a threatened pregnancy indefinitely; research has demonstrated that a gain of 24 hours to several days is the best outcome that can be expected (Goldenberg & Rouse, 1998; Maloni, 2000). It is now thought that the best reason to use tocolytics is that they afford the opportunity to begin administering antenatal glucocorticoids to accelerate fetal lung maturity and reduce the severity of sequelae in infants born preterm (Enkin et al., 2001; Goldenberg & Rouse, 1998).
The use of tocolysis to suppress preterm labor has increased 50%, from 1.6% in 1990 to 2.4% in 1999 (Ventura et al., 2001). The medications most commonly used for this purpose are magnesium sulfate, ritodrine, terbutaline, indomethacin, and nifedipine. Ritodrine is the only medication approved by the U.S. Food and Drug Administration (FDA) specifically for the purpose of cessation of uterine contractions. The other drugs are used for this purpose on an "unlabeled" basis (i.e., drugs known to be effective for a specific purpose though not specifically developed and tested for this purpose). There are important contraindications to the use of all tocolytics (Box 7). Because these medications have the potential for serious adverse reactions for mother and fetus, close nursing supervision during treatment is critical (Lehne, 2001) (Box 8 and Table 1).
BOX 7 Contraindications to Tocolysis
Severe pregnancy-induced hypertension or eclampsia
Active vaginal bleeding
Medical or obstetric condition that contraindicates continuation
Estimated gestational age over 37 weeks
Dilation over 4 cm
Lethal fetal anomaly
Acute fetal distress
BOX 8 Nursing Care for Women Receiving Tocolytic Therapy
Explain the purpose and side effects of tocolytic therapy to woman and her family.
Position woman on her side to enhance placental perfusion and reduce pressure on the cervix.
Monitor maternal vital signs, FHR, and labor status according to hospital protocol and professional standards.
Assess mother and fetus for signs of adverse reactions related to the tocolytic being administered.
Determine maternal fluid balance by measuring daily weight and intake and output (I&O).
Limit fluid intake to 2500 to 3000 ml/day, especially if a beta-adrenergic agonist is being administered.
Provide psychosocial support and opportunities for women and family to express feelings and concerns.
Offer comfort measures as required.
Encourage diversional activities and relaxation techniques.
Table 1 Medication Guide: Tocolitic Therapy for preterm Labor
DOSAGE AND ROUTE
Ritodrine (Yutopar) Beta-adrenergic agonist
Relaxes smooth muscles, inhibiting uterine activity and causing bronchodilation
Mix 150 mg in 500 ml isotonic intravenous solution
Attach to controller pump and piggyback to primaryinfusion
Begin infusion at 0.05 to 0.1 mg/min Increase rate by 0.05 mg q10min until contractions stop, intolerable adverse reactions develop, or a maximum dose of 0.35 mg/min is reached
Maintain effective dose for 12 to 24 hr
Intravenous adverse reactions:
• Shortness of breath, coughing, tachypnea, pulmonary edema
• Tachycardia, palpitations, skipped beats
• Chest pains
• Tremors, dizziness, nervousness
• Muscle cramps and weakness
• Hyperglycemia; hypokalemia
• Nausea and vomiting
• Fetal tachycardia Oral adverse reactions:
• Significant adverse effects are rare
• Gl distress
Women should be screened with ECG before therapy begins; maternal heart disease and hypertension are contraindications
Use cautiously if woman has type 1 diabetes or hyperthyroidism
Validate that woman is in PTL and is over 20 weeks of gestation
Assess woman and fetus before and after each rate increase and following frequency of agency protocol
Discontinue infusion and notify physician if
• Maternal heart rate greater than 120 to 140 beats/min; dysrhythmias, chest pain
• BP is less than 90/60 mm Hg
• Fetal heart rate greater than 180 beats/min
Ensure that propranolol (Inderal) is available to reverse adverse effects related to cardiovascular function
Relaxes smooth muscles, inhibiting uterine activity and causingbronchodilation
• 0.25 mg q30min for 2 hr
• Maximum dose: 0.5 mg q4-6h
• Maintenance dose 0.05-0.1 mg/hr
• Bolus: 0.25 mg q4-6h according to contraction pattern
• 3 mg/24 hr
Similar to ritodrine
Teach woman and family:
• Assessment measures: pulse, BP, respiratory effort, insertion site for infection, signs of PTL and adverse reactions of terbutaline
• Who to call if problems or concerns arise
• Site care and pump
• Activity restrictions Arrange for follow-up
CNS depressant; relaxes smooth muscles including uterus
Mix 40 g in 1000 ml intravenous solution, piggyback to primary infusion, and administer loading dose or bolus of 4-6 g using controller pump over 15 to 20 min
Continue maintenance infusion at 1 g/hr, increasing to a maximum 3 g/hr until contractions stop or intolerable adverse reactions develop
During loading dose:
• Hot flushes, sweating, nausea and vomiting, drowsiness, and blurred vision; usually subside when loading dose is completed
Intolerable adverse reactions:
• Respiratory rate less than 12 breaths/min
• Absent DTRs
• Severe hypotension
• Extreme muscle weakness
• Urine output less than 25-30 ml/hr
• Serum magnesium level of 10 mEq/L or greater
Assess woman and fetus before and after each rate increase and following frequency of agency protocol Monitor serum magnesium levels; therapeutic level should range between 4 and 7.5 mEq/L
Discontinue infusion and notify physician if intolerable adverse reactions occur
Ensure that calcium gluconate is available for emergency administration to reverse magnesium sulfate toxicity
Limit IV fluid intake to 125 ml/hr
Calcium channel blocker; relaxes smooth muscles including the uterus by blocking calcium entry
nitial dose: 10-20 mg
Maintenance dose: 10 to 20 mg q4-6h PO
Transient tachycardia, palpitations
Do not use with magnesium
Assess woman and fetus according to agency protocol being alert for adverse reactions
Do not use sublingual route
Prostaglandin inhibitor; relaxes uterine smooth muscle
Initial dose: 50 mg (orally or rectally)
Maintenance dose: 25-50 mg, q4-6h for 24-48 hr (PO)
Maternal: nausea and vomiting, dyspepsia, dizziness, oligohyramnios
Fetal: premature closure of ductus arteriosus
Neonate: bronchopulmonary dysplasia, respiratory distress syndrome, intracranial hemorrhage, necrotizing enterocolitis, hyperbilirubinemia
Used when other methods fail; never used after 35 weeks of gestation
Do not use for women with bleeding potential
Fetal assessment: amniotic fluid level; function of ductus arteriosus
Magnesium sulfate is the most commonly used tocolytic agent, although its exact mechanism of action on uterine muscle is unclear. Because it acts as a central nervous system depressant, it has been used for decades for seizure control in women with preeclampsia; it began to be used for tocolysis in the 1970s (lams, 2002). At the onset of preterm labor, magnesium sulfate is administered via an intravenous infusion. Terbutaline, 0.25 mg, may be injected subcutaneously before the initiation of the magnesium sulfate infusion and then administered again by subcutaneous pump as the infusion is discontinued (see Table 1).
Ritodrine and terbutaline, beta-adrenergic agonist medications for tocolysis, work by relaxing smooth muscle. When used, ritodrine is usually administered intravenously as one of the first steps in suppressing preterm labor. Terbutaline is most commonly administered by a subcutaneous injection of 0.25 mg to suppress uterine hyperactivity or by a subcutaneous pump. Effectiveness of pump therapy in prolonging gestation is controversial (Guinn et al., 1998). Beta-adrenergic agonists have many maternal and fetal side effects and must always be used with extreme caution and careful, conscientious nursing care. Medication administration and nursing care are aimed at maintaining a therapeutic level of medication and avoiding the most serious side effects while maintaining optimal health of the fetus (see Table 1).
NURSE ALERT! Caution must be used when administering intravenous fluids to women in preterm labor because this practice can increase the risk for tocolyticinduced pulmonary edema, especially when a betaadrenergic agonist is used. It is recommended that the total oral and intravenous fluid intake in 24 hours should be restricted to 2400 to 3000 ml. Strict intake and output measurement, daily weight determination, and assessment of pulmonary function should be instituted (American College of Obstetricians and Gynecologists [ACOG], 1995a; Freda & DeVore, 1996; Hill, 1995).
Indomethacin, a nonsteroidal antiinflammatory medication, has been shown in some trials to cause a cessation of uterine contractions by blocking the action of prostaglandins (Besinger et al, 1991; Lehne, 2001). The severity of fetal side effects associated with the use of indomethacin for tocolysis makes it less common than other classes of tocolytic drugs. However, Macones and Robinson (1998) studied the risk of using indomethacin versus the benefit of delayed birth in 1000 women and found that it was more beneficial to the fetus for the mother to have received indomethacin and the fetus to have gained gestational age than was preterm birth at 32 weeks (see Table 1).
Nifedipine, a calcium channel blocker, is another tocolytic agent that can suppress contractions (Lehne, 2001; Read & Wellby, 1986). It works by inhibiting calcium from entering smooth muscle cells, thus reducing uterine contractions. Despite mild maternal side effects, this medication might be used less than other tocolytic agents because of concerns about fetal side effects. When the tocolytic effects and maternal tolerance of nifedipine and ritodrine were compared, no significant differences in length of delay of birth were found, but significantly fewer maternal side effects occurred with nifedipine (Garcia-Velasco & Gonzalez-Gonzalez, 1998) (see Table 1).
Promotion of fetal lung maturity
Antenatal glucocorticoids. Antenatal glucocorticoids given as intramuscular injections to the mother accelerate fetal lung maturity. It is viewed as a form of care
likely to be beneficial (Enkin et al., 2001). This class of medications also seems to decrease rates of intraventricular hemorrhage in preterm infants (Goldenberg & Rouse, 1998). All women between 24 and 34 weeks of gestation should be given antenatal glucocorticoids when preterm birth is threatened, unless there is a medical indication for immediate delivery such as cord prolapse, chorioamnionitis, or abruptio placentae. The regimen for administration of antenatal glucocorticoids is given in the Medication Guide.
Medication Guide Antenatal Glucocorticoid Therapy with Betamethasone, Dexamethasone
Stimulates fetal lung maturation by promoting release of enzymes that induce production or release of lung surfactant. NOTE: The FDA has not approved these medications for this use (i.e., this is an unlabeled use for obstetrics).
To prevent or reduce the severity of respiratory distress syndrome in preterm infants between 24 and 34 weeks of gestation
DOSAGE AND ROUTE
Betamethasone: 12 mg IM x 2 doses 12 hr apart
Dexamethasone: 6 mg IM x 2 doses 12 hr apart
May be repeated in 7 days if birth has not occurred.
Possible maternal infection, pulmonary edema (if given with /3-adrenergic medications), may worsen maternal condition (diabetes, hypertension)
Give deep IM in gluteal muscle. Teach signs of pulmonary edema. Assess blood glucose levels and lung sounds. Do not give if woman has infection. Use in women with PPROM not universally recommended.
Management of inevitable preterm birth
Labor that has progressed to a cervical dilation of 4 cm is likely to lead to inevitable preterm birth. Preterm births in tertiary care centers lead to better neonatal and maternal outcomes. Women considered at risk for inevitable preterm birth should be transferred quickly to such a facility to ensure the best possible outcome. The first dose of antenatal glucocorticoids should be given before transfer because these medications require 24 hours to take effect.
Although maternal transport helps ensure a better health outcome for the mother and the baby, it may have complications. Women may be transported to tertiary care centers far from home, making visits by the family difficult and increasing the anxiety levels of the woman and her family.
Evaluation of the nursing care provided for a woman at risk for preterm birth is based on the expected outcomes of care (see Plan of Care).
PLAN OF CARE Preterm Labor
NURSING DIAGNOSIS Deficient knowledge related to recognition of preterm labor
Expected Outcome Woman and significant other delineate the signs and symptoms of preterm labor.
Assess what the partners know about abnormal signs and symptoms during pregnancy to identify areas of deficit.
Discuss signs and symptoms that serve as warning signs of preterm labor so that the woman or her partner has adequate information to identify problems early.
Provide written supplemental materials that include a list of warning signs and instructions regarding what to do if any of the listed signs occur so that the couple can reinforce and review learning and act swiftly and appropriately should a sign occur.
Discuss and demonstrate how to assess and time the contractions to provide needed skills to assess the signs of labor.
NURSING DIAGNOSIS Risk for maternal/fetal injury related to recurrence of preterm labor
Expected outcomes Woman demonstrates ability to assess self and fetus for signs of recurring labor; maternal-fetal well-being is maintained.
Teach woman/partner how to monitor fetal and uterine contraction activity daily to provide immediate evidence of a worsening condition.
Have woman/partner report rupture of membranes, vaginal bleeding, cramping, pelvic pressure, or low backache to appropriate health care resource immediately because such symptoms are signs of labor.
If home uterine activity monitoring is to be used, teach woman/partner how to use the monitoring device and how to transmit the data to the health care provider via telephone to enhance correct use of monitoring device and increase the accuracy of detection of early labor.
Have woman monitor her weight, diet, fluid intake, and vital signs on a daily basis to evaluate for potential problems.
Limit activities to bed rest with bathroom privileges to decrease the likelihood of onset of labor.
Use a side-lying position to enhance placental perfusion.
Abstain from sexual intercourse and nipple stimulation because such activities may stimulate uterine contractions.
Practice relaxation techniques to decrease uterine tone and decrease anxiety and stress.
Take tocolytic or other medications per physician's orders to inhibit uterine contractions.
Teach woman/partner about and have them report any medication side effects immediately to prevent medicationinduced complications.
Have family arrange for alternative strategies in carrying out the woman's usual roles and functions to decrease stress and limit temptations to increase activity.
If small children are part of the household, encourage family to make alternative arrangements for child care to enhance woman's adherence to bed rest protocol.
NURSING DIAGNOSIS Anxiety related to preterm labor and potentially premature neonate
Expected outcome Feelings and symptoms of fear/anxiety abate.
Provide a calm, soothing atmosphere and teach family to provide emotional support to facilitate coping.
Encourage verbalization of fears to decrease intensity of emotional response.
Involve woman and family in the home management of her condition to promote a greater sense of control.
Help the woman identify and use appropriate coping strategies and support systems to reduce fear/anxiety.
Explore the use of desensitization strategies such as progressive muscle relaxation, visual imagery, or thought stopping to reduce fear-related emotions and related physical symptoms.
NURSING DIAGNOSIS Deficient diversions! Activity related to imposed bed rest
Expected outcome Verbalization of diminished feelings of boredom.
Assist woman to creatively explore personally meaningful activities that can be pursued from the bed to ensure activities that have meaning, purpose, and value to the individual.
Maintain emphasis on personal choices of the woman because doing so promotes control and minimizes imposition of routines by others.
Evaluate what support and system resources are available in the environment to assist in providing diversional activities.
Explore ways for the woman to remain an active participant in home management and decision making to promote control.
Engage support of family and friends in carrying out chosen activities and making necessary environmental alterations to ensure success.
Teach woman about stress management and relaxation techniques to help manage tension of confinement.
PRETERM PREMATURE RUPTURE OF MEMBRANES
Premature rupture of membranes (PROM) is the rupture of the amniotic sac and leakage of amniotic fluid beginning at least 1 hour before the onset of labor at any gestational age. Preterm premature rupture of membranes (PPROM) (i.e., membranes rupture before 37 weeks of gestation) occurs in up to 25% of all cases of preterm labor. Infection often precedes PPROM, but the etiology of PPROM remains unknown. PPROM is diagnosed after the woman complains of either a sudden gush of fluid from the vagina or a slow leak of fluid from the vagina.
Infection is the serious side effect of PPROM that makes it a major complication of pregnancy. Chorioamnionitis is an intraamniotic infection of the chorion and amnion that is potentially life threatening for the fetus and the woman. Most cases of intrauterine infection respond well to antibiotics, yet sepsis can occur and can lead to maternal death. Fetal complications from chorioamnionitis include congenital pneumonia, sepsis, and meningitis (Mercer & Lewis, 1997). Even in the absence of infection, PPROM can precipitate cord prolapse or cause oligohydramnios leading to cord compression, potentially lifethreatening complications for the fetus.
When PPROM is suspected, strict sterile technique should be used in any vaginal examination to avoid introduction of infection. A Nitrazine or fern test is used to determine whether the discharge is amniotic fluid (see Chapter 14, Procedure Box: Tests for Rupture of Membranes, p. 326). A woman with this diagnosis is often cared for at home, with more frequent visits to her physician or nurse-midwife. Expectant management will continue as long as there are no signs of infection or fetal distress. Nursing support of the woman and her family is critical at this time. She is often anxious about the health of her baby and may fear that she was responsible in some way for the membrane rupture. The nurse needs to encourage expression of feelings and concerns, provide information, and make referrals as needed (Weitz, 2001).
Frequent biophysical profiles are performed to determine fetal health status and estimate amniotic fluid volume. The woman with PPROM should also be taught how to count fetal movements daily because a slowing of fetal movement has been shown to be a precursor to severe fetal compromise. Several methods are commonly used to count fetal movements; one method for fetal movement counting is described in the Self-Care box (Freda et al., 1993). Antenatal glucocorticoids may be administered if chorioamnionitis is absent (ACOG, 1998; Weitz, 2001).
Vigilance for signs of infection is a major part of the nursing care and patient education following PPROM. The woman needs to be taught how to keep her genital area clean and that nothing should be introduced into her vagina. Signs of infection (e.g., fever, foul-smelling vaginal discharge, rapid pulse) should be reported to the physician or nurse-midwife immediately. Prophylactic antibiotic therapy may be ordered because it improves perinatal outcome (ACOG, 1998).
POSTTERM PREGNANCY, LABOR, AND BIRTH
A postterm pregnancy, or prolonged pregnancy, is one that extends beyond the end of week 42 of gestation, or 294 days from the first day of the last menstrual period. The incidence of postterm pregnancy is estimated to be between 4% and 14%, with an average of 10% (Cunningham et al, 2001).
Many pregnancies are misdiagnosed as prolonged. This can occur because (1) the pregnancy is inaccurately dated because the woman has an irregular menstrual cycle pattern, (2) an accurate date of the last menstrual period is unknown, or (3) entry into prenatal care was delayed or did not occur. Interestingly, a woman who experiences one postterm pregnancy is 30% to 40% more likely to experience it again in subsequent pregnancies (Arulkumarian, 1997).
Clinical manifestations of postterm pregnancy include maternal weight loss, decreased uterine size, meconium in the amniotic fluid, and advanced bone maturation of the fetal skeleton with an exceptionally hard fetal skull (Gilbert & Harmon, 1998).
MATEMAL AND FETAL RISKS
Maternal risks are often related to the birth of an excessively large infant. The woman is at increased risk for dysfunctional labor; birth canal trauma, including lacerations and extension of episiotomy related to vaginal birth; postpartum hemorrhage; and infection. Interventions such as induction of labor with oxytocin, forcepsor vacuum-assisted birth, and cesarean birth are more likely to be necessary. The woman also may experience fatigue and psychologic reactions such as depression, frustration, and feelings of inadequacy as she passes her estimated date of birth (Arulkumarian, 1997; Freeman & Lagrew, 1996; Gilbert & Harmon, 1998).
Fetal risks appear to be twofold. The first is the possibility of prolonged labor, shoulder dystocia, birth trauma, and asphyxia from macrosomia. Macrosomia occurs when the placenta continues to provide adequate nutrients to support fetal growth after 40 weeks of gestation. It is estimated to occur in approximately 25% of prolonged pregnancies (Divon, 2002). The second risk is the compromising effects on the fetus of an "aging" placenta. Spellacy (1999) notes that placental function gradually decreases after 37 weeks of gestation. Amniotic fluid volume (AFV) declines to approximately 800 ml by 40 weeks of gestation and to approximately 400 ml by 42 weeks of gestation. The resulting oligohydramnios can lead to fetal hypoxia related to cord compression. If placental insufficiency is present, there is a high likelihood of fetal distress occurring during labor. Neonatal problems may include asphyxia, meconium aspiration syndrome, dysmaturity syndrome, hypoglycemia, polycythemia, and respiratory distress (Gilbert & Harmon, 1998).
The management of postterm pregnancy is still controversial. The induction of labor at 41 to 42 weeks is suggested by some authorities as a means of reducing the rate of cesarean birth and stillbirth or neonatal death (Hannah et al., 1996). Others follow a more individualized approach, allowing the pregnancy to proceed to 43 weeks of gestation as long as assessment of fetal well-being using a combination of tests is performed and the results of the tests are normal (Searing, 2001).
LEGAL TIP Informed Consent Regarding Care During Postterm Pregnancy
The woman with a postterm pregnancy should be informed about the risks and benefits of both treatment and nontreatment. The standard of practice for postterm pregnancy is to begin antepartal surveillance (e.g., maternal assessments and tests of fetal well-being) by 14 days after the EDB, no matter how the date was derived. The woman and her physician or nursemidwife should mutually agree on a plan of care (Wood, 1994).
Antepartum assessments for postterm pregnancy may include daily fetal movement counts, nonstress tests, amniotic fluid volume assessments, contraction stress tests, biophysical profiles, and Doppler flow measurements. The woman and her family should be fully informed regarding the tests performed and the meaning of the results obtained.
The amniotic fluid index should be greater than 8 with at least one pocket of amniotic fluid greater than 2 cm, and amniotic fluid should be present throughout the uterine cavity (Gilbert & Harmon, 1998; Schmidt, 1999). The biophysical profile may be the best way of gauging fetal well-being because it combines nonstress testing with realtime ultrasound scanning to assess fetal movements, fetal breathing movements, and the AFV. Determining the AFV is critical in women with postterm pregnancies because a decreased AFV (i.e., oligohydramnios) has been associated with fetal stress as a result of umbilical cord compression.
Cervical checks usually are performed weekly after 40 weeks of gestation to determine whether the condition of the cervix is favorable for induction (9 or greater on the Bishop score) (see Table 4). Vaginal secretions may be assessed for the amount of fetal fibronectin; however results of studies have been inconclusive (Divon, 2002). Amniocentesis or amnioscopy may be performed to detect meconium in the amniotic fluid (Spellacy, 1999).
During the postdate period the woman is encouraged to assess fetal activity daily, assess for signs of labor, and keep appointments with her physician or nurse-midwife (see Self-Care box). The woman and her family should be encouraged to express their feelings about the prolonged pregnancy. Referral to a support group or another supportive resource may be needed (Schmidt, 1999).
Patient Instructions for Self-Care Postterm Pregnancy
Perform daily fetal movement counts.
Assess for signs of labor.
Call your primary health care provider if your membranes rupture, or if you perceive a decrease in or no fetal movement.
Keep appointments for fetal assessment tests or cervical checks.
Come to the hospital soon after labor begins.
If the woman's cervix is ripe, labor is usually induced with oxytocin. If her cervix is not ripe, continued fetal surveillance or a cervical ripening agent (e.g., prostaglandin insert or gel) may be administered followed by oxytocin induction (Gilbert & Harmon, 1998; Schmidt, 1999).
The fetus of a woman with a postterm pregnancy should be monitored electronically for a more accurate assessment of the FHR pattern. If oligohydramnios is pre sent, amnioinfusion may be implemented to restore amniotic fluid volume and thereby maintain a cushioning of the cord. Inadequate fluid volume leads to compression of the cord, which results in fetal hypoxia that is reflected in variable or prolonged deceleration patterns and passage of meconium. Amnioinfusion may also be used to prevent or minimize meconium aspiration syndrome by diluting amniotic fluid thickened with meconium passed by a hypoxic fetus. Maternal-fetal risks related to amnioinfusion, although rare, can result from infection and overdistention of the uterine cavity with infused fluid (Folsom, 1997; Gilbert & Harmon, 1998; Schmidt, 1997). Accurate assessment of the woman's labor pattern also is important because dysfunctional labor is common (Spellacy, 1999).
Emotional support is essential for the woman with a postterm pregnancy and her family. A vaginal birth is anticipated, but the couple should be prepared for a forcepsassisted, vacuum-assisted, or cesarean birth if complications arise.
Assessment and Nursing Diagnoses
Risk assessment is a continuous process in the laboring woman. Review of the findings obtained during the initial interview conducted at the woman's admission to the labor unit and ongoing observations of her psychologic response to labor may reveal factors that can be a source of dysfunctional labor. These factors may include anxiety or fear, a complication of pregnancy, or previous labor complications. The initial physical assessment and ongoing assessments provide information about maternal well-being; status of labor in terms of the characteristics of uterine contractions and progress of cervical effacement and dilation; fetal well-being in terms of FHR and pattern, presentation, station, and position; and status of the amniotic membranes. Ultrasound scanning can identify potential dysfunctional labor problems related to the fetus or maternal pelvis. All these assessments contribute to accurate identification of potential and actual nursing diagnoses related to dystocia and maternal-fetal compromise.
Nursing diagnoses that might be identified in women experiencing dystocia include the following:
• Risk for maternal or fetal injury related to
-interventions implemented for dystocia
• Powerlessness related to
-loss of control
• Risk for infection related to
-rupture of membranes
• Ineffective coping related to
-lack of support system
Expected Outcomes of Care
Expected outcomes for the woman who is experiencing dystocia include that the woman will do the following:
• Understand the causes and treatment of dysfunctional labor
• Use measures recommended by the obstetric care team to enhance the progress of labor and birth
• Express relief of pain
• Experience labor and birth with minimal or no complications, such as infection, injury, or hemorrhage
• Give birth to a healthy infant who has not experienced fetal distress
Plan of Care and Interventions
Nurses assume many caregiving roles when labor is complicated. They also work collaboratively with other health care providers in providing care. Interventions that the nurse may implement or assist with include external cephalic version, trial of labor, induction or augmentation with oxytocin, amniotomy, and operative procedures. The nursing role is identified with each of the procedures described.
LEGAL TIP Standard of Care—Labor and Birth Complications
• Document all assessment findings, interventions, and patient responses on patient record and monitor strips according to unit protocols, procedures, and policies and professional standards.
• Assess whether the woman (and her family, if appropriate) is fully informed about procedures for which she is consenting.
• Maintain safety in administering medications and treatments correctly.
• Have verbal orders signed as soon as possible.
• Provide care at the acceptable standard (e.g., according to hospital protocols and professional standards).
• If short staffing occurs in the unit and the nurse is assigned additional patients, the nurse should document that rejecting this additional assignment would have placed these patients in danger as a result of abandonment.
• Maternal and fetal monitoring continues until birth according to the policies, procedures, and protocols of the birthing facility, even when a decision to carry out cesarean birth is made.
Version is the turning of the fetus artificially from one presentation to another and may be done either externally or internally.
External cephalic version. External cephalic version (ECV) is used to attempt to turn the fetus from a breech or shoulder presentation to a vertex presentation for birth. It may be attempted in a labor and birth setting after 37 weeks of gestation. Before it is attempted, ultrasound scanning is done to determine the fetal position; locate the umbilical cord; rule out placenta previa; and assess the amount of amniotic fluid, the fetal age, and the presence of any anomalies. A nonstress test is performed to confirm fetal wellbeing, or the FHR pattern is monitored for a time (usually 10 to 20 minutes). Informed consent is obtained. Contraindications to ECV include uterine anomalies, previous cesarean birth, CPD, placenta previa, multifetal gestation, and oligohydramnios (Cunningham et al., 2001; Laros, Flanagan, & Kilpatrick, 1995).
ECV is accomplished by the exertion of gentle, constant pressure on the abdomen (Fig. 7). A tocolytic agent, such as magnesium sulfate or terbutaline, often is given to relax the uterus and facilitate the maneuver. Ultrasound scanning is done to identify potential problems, such as cord entanglement and placental separation (Cunningham et al., 2001; Laros, Flanagan, & Kilpatrick, 1995).
Fig. 7 External version of fetus from breech to vertex presentation. This must be achieved without force. A, Breech is pushed up out of pelvic inlet while head is pulled toward inlet. B, Head is pushed toward inlet while breech is pulled upward.
During an attempted ECV, the nurse continuously monitors the FHR, especially for bradycardia; checks the maternal vital signs; and assesses the woman's level of comfort because the procedure may cause discomfort. After the procedure is completed, the nurse continues to monitor maternal vital signs, uterine activity, and FHR and assess for vaginal bleeding until the woman's condition is stable. Women who are Rh negative should receive Rh immune globulin because the manipulation can cause fetomaternal bleeding (Cunningham et al., 2001; Laros, Flanagan, & Kilpatick, 1995).
Internal version. With internal version, the fetus is turned by the physician, who inserts a hand into the uterus and changes the presentation to cephalic (head) or podalic (foot). Internal version may be used in multifetal pregnancies to deliver the second fetus. The safety of this procedure has not been documented; maternal and fetal injury is possible. Cesarean birth is the usual method for managing malpresentation in multifetal pregnancies. The nurse's role is to monitor the status of the fetus and to provide support to the woman.
Trial of labor
A trial of labor (TOL) may be initiated if the mother's pelvis is of questionable size or shape, if the fetus is in an abnormal presentation, or if she wishes to have a vaginal birth after a previous cesarean birth. It is a form of care likely to be beneficial when implemented after a previous low segment cesarean birth (Enkin et al., 2001). Fetal sonography or maternal pelvimetry may be done before a TOL to rule out CPD. The cervix must be soft and dilatable. During TOL, the woman is evaluated for the occurrence of active labor, including adequate contractions, engagement and descent of the presenting part, and effacement and dilation of the cervix. Nurses must recognize that the woman and her partner are often anxious about her health and well-being and that of their baby. Supporting and encouraging the woman and her partner and providing information regarding progress can reduce stress, enhance the labor process, and facilitate a successful outcome.
Induction of labor
Induction of labor is the chemical or mechanical initiation of uterine contractions before their spontaneous onset for the purpose of bringing about the birth. In 1999 approximately 20% of women who gave birth had their labors induced, a doubling of the labor induction rate in 1990 (Ventura et al., 2001). Induction may be indicated for a variety of medical and obstetric reasons. These include pregnancy-induced hypertension, diabetes mellitus and other medical problems, postterm gestation, suspected fetal jeopardy (e.g., IUGR), logistic factors such as history of previous rapid birth or distance of the woman's home from the hospital, and fetal death. Under such conditions, the risk to the mother or fetus is less than the risk of continuing the pregnancy (Mathews, 1998).
Both chemical and mechanical methods are used to induce labor. Intravenous oxytocin and amniotomy are the most common methods used in the United States. Less commonly used methods include nipple stimulation (manual or with a breast pump), the ingestion of castor oil or herbal preparations, a soap-suds enema, stripping of the membranes, and acupuncture (Summers, 1997). Prostaglandins are also used for inducing labor, but their use for this purpose continues to be investigated (Mastrogiannis & Knuppel, 1995; Summers, 1997).
Success rates for induction of labor are higher when the condition of the cervix is favorable, or inducible. A rating system such as the Bishop score (Table 4) can be used to evaluate inducibility. For example, a score of 9 or more on this 13-point scale might indicate that the cervix is soft (2), anterior (2), 50% or more effaced (1), and dilated 2 cm or more (1) and that the presenting part is engaged (3). Induction of labor is likely to be more successful if the score is 9 or more (Cunningham et al., 2001).
TABLE 4 Bishop Score
+ 1, +2
Cervical ripening methods
Chemical agents. A prostaglandin E2 gel has been approved by the FDA since 1993 as a cervical ripening agent. Currently, preparations of prostaglandin Ej and prostaglandin E2 can used before induction to "ripen" (soften and thin) the cervix (see Medication Guides). This treatment usually results in a higher success rate for the induction of labor, the need for lower dosages of oxytocin during the induction, and shorter induction times. In some cases, women will go into labor after the administration of prostaglandin, thereby eliminating the need to administer oxytocin to induce labor (ACOG, 1995b; Gilbert & Harmon, 1998; Mundle & Young, 1996; Simpson & Poole, 1998; Summers, 1997; Wilson, 2000).
Cervical Ripening Using Prostagiandin E, (PGE-,): Misoprostol CCytotec)
PGE, ripens the cervix, making it softer and causing it to begin to dilate and efface; stimulates uterine contractions.
PGE, is used for preinduction cervical ripening (ripen cervix before oxytocin induction of labor when the Bishop score is 4 or less) and to induce labor or abortion
Insert 25 to 50 jxg (1/4 to 1/2 of a 100-/u,g tablet) intravaginally into the posterior fornix using the tips of index and middle fingers without the use of a lubricant. Repeat every 4 to 6 hours as needed to a maximum of 300 to 400 ;u,g in a 24-hour period or until an effective contraction pattern is established (3 or more uterine contractions in 10 minutes), cervix ripens (Bishop score of 8 or greater), or significant adverse reactions occur.
Administer: 50-100 /xg, PO q4-6h (Gl effects increased; may be less effective)
Higher dosages are more likely to result in adverse reactions such as nausea and vomiting, diarrhea, fever, tachysystole (12 or more uterine contractions in 20 minutes without alteration of FHR pattern), hyperstimulation of the uterus (tachysystole with nonreassuring FHR patterns), or fetal passage of meconium.
• Explain procedure to woman and her family. Ensure that an informed consent has been obtained as per agency policy.
• Assess maternal-fetal unit, before each insertion and during treatment following agency protocol for frequency.
Assess maternal vital signs and health status, FHR pattern, and status of pregnancy, including indications for cervical ripening or induction of labor, signs of labor or impending labor, and the Bishop score. Recognize that a nonreassuring FHR pattern; maternal fever, infection, vaginal bleeding, or hypersensitivity; and regular, progressive uterine contractions contraindicate the use of misoprostol.
• Use caution if the woman has a history of asthma, glaucoma, or renal, hepatic, or cardiovascular disorders.
• Have woman void before procedure.
• Assist woman to maintain a supine position with lateral tilt or a side-lying position for 30 to 40 minutes after insertion.
• Prepare to swab vagina to remove unabsorbed medication using a saline soaked gauze wrapped around fingers and to administer terbutaline 0.25 mg subcutaneously or intravenously if significant adverse reactions occur.
• Initiate oxytocin for induction of labor 2 to 4 hours after last dose of misoprostol was administered, following agency protocol, if ripening has occurred and labor has not begun.
• Document all assessment findings and administration procedures.
Misoprostol (Cytotec) has not yet been approved by the FDA for cervical ripening or labor induction.
Cervical Ripening Using Prostaglandin E2 (PGE2): Dinoprostone (Cervidil Insert; Prepidil Gel)
PGE2 ripens the cervix, making it softer and causing it to begin to dilate and efface; stimulates uterine contractions.
PGE2 is used for preinduction cervical ripening (ripen cervix before oxytocin induction of labor when the Bishop score is 4 or less), and to induce labor or abortion (abortifacient agent)
Place Cervidil insert (10 mg dinoprostone gradually released over 12 hours) intravaginally into the posterior fornix. Insert Prepidil gel (2.5-ml syringe containing 0.5 mg of dinoprostone) into cervical canal just below internal cervical os. Repeat gel insertion in 6 hours as needed to a maximum of 1.5 mg in a 24-hour period.
Continue treatment until maximum dosage is administered or until an effective contraction pattern is established (3 or more uterine contractions in 10 minutes), cervix ripens (Bishop score of 8 or greater), or significant adverse reactions occur.
Potential adverse reactions include headache, nausea and vomiting, diarrhea, fever, hypotension, tachysystole (12 or more uterine contractions in 20 minutes without alteration of FHR pattern), hyperstimulation of the uterus (tachy- systole with nonreassuring FHR patterns), or fetal passage of meconium.
• Explain procedure to woman and her family. Ensure that an informed consent has been obtained as per agency policy.
• Assess maternal-fetal unit, before each insertion and during treatment following agency protocol for frequency. Assess maternal vital signs and health status, FHR pattern, and status of pregnancy, including indications for cervical ripening or induction of labor, signs of labor or impending labor, and the Bishop score. Recognize that a nonreassuring FHR pattern; maternal fever, infection, vaginal bleeding, or hypersensitivity; and regular, progressive uterine contractions contraindicate the use of dinoprostone.
• Use caution if the woman has a history of asthma; glaucoma; or renal, hepatic, or cardiovascular disorders.
• Bring gel to room temperature before administration. Do not force warming process by using a warm water bath or other source of external heat (e.g., microwave).
• Have woman void before insertion.
• Assist woman to maintain a supine position with lateral tilt or a side-lying position for 30 to 60 minutes after insertion of gel or for 2 hours after placement of insert.
• Prepare to swab vagina to remove remaining gel using a saline-soaked gauze wrapped around fingers or pull string to remove insert and to administer terbutaline 0.25 mg subcutaneously or intravenously if significant adverse reactions occur.
• Initiate oxytocin for induction of labor within 6 to 12 hours after last instillation of gel or within 30 minutes after removal of the insert.
• Follow agency protocol for induction if ripening has occurred and labor has not begun.
• Document all assessment findings and administration procedures.
Dinoprostone is the only FDA-approved medication for cervical ripening or labor induction.