Assessment for Risk Factors

Assessment for Risk Factors

Prepared by assistant professor N.Petrenko, MD, PhD

LEARNING OBJECTIVES

• Explore physiologic and psychologic aspects of high risk pregnancy.

• Discuss regionalization of health care services.

• Examine risk factors identified through history, physical examination, and diagnostic techniques.

• Describe diagnostic techniques and the implications of findings.

• Develop a teaching plan to explain diagnostic techniques to patients and their families.

 

KEY TERMS AMD DEFINITIONS

acoustic stimulation test Antepartum test to elicit fetal heart rate response to sound; performed by applying sound source (laryngeal stimulator) to maternal abdomen over the fetal head

alpha-fetoprotein (AFP) Fetal antigen; elevated levels in amniotic fluid and maternal blood are associated with neural tube defects

amniocentesis Procedure in which a needle is inserted through the abdominal and uterine walls to obtain amniotic fluid; used for assessment of fetal health and maturity

amniotic fluid index (AFI) Estimation of amount of amniotic fluid by means of ultrasound to determine excess or decrease

biophysical profile (BPP) Noninvasive assessment of the fetus and its environment using ultrasonography and fetal monitoring; includes fetal breathing movements, gross body movements, fetal tone, reactive fetal heart rate, and qualitative amniotic fluid volume

chorionic villus sampling (CVS) Removal of fetal tissue from placenta for genetic diagnostic studies

contraction stress test (CST) Test to stimulate uterine contractions for the purpose of assessing fetal response; a healthy fetus does not react to contractions, whereas a compromised fetus demonstrates late decelerations in the fetal heart rate that are indicative of uteroplacental insufficiency

daily fetal movement count (DFMC) Maternal assessment of fetal activity; the number of fetal movements within a specified time are counted; also called "kick count"

Doppler blood flow analysis Use of ultrasound for noninvasive measurement of blood flow in the fetus and placenta

magnetic resonance imaging (MRI) Noninvasive nuclear procedure for imaging tissues with high fat and water content; in obstetrics, uses include evaluation of fetal structures, placenta, and amniotic fluid volume

nonstress test (NST) Evaluation of fetal response (fetal heart rate) to natural contractile uterine activity or to an increase in fetal activity

percutaneous umbilical blood sampling (PUBS) Procedure during which a fetal umbilical vessel is accessed for blood sampling or for transfusions

uteroplacental insufficiency (UPI) Decline in placental function (exchange of gases, nutrients, and wastes) leading to fetal hypoxia and acidosis;evidenced by late decelerations of the fetal heart rate in response to uterine contractions

 

Approximately 500,000 of the 4 million births that occur in the United States each year are categorized as high risk because of maternal or fetal complications. Identification of the risks, together with appropriate and timely intervention during the perinatal period, can prevent morbidity and mortality among mothers and infants.

With the changing demographics in the United States, more women and families can be identified as at risk because of factors other than biophysical criteria. The increasing numbers of homeless, single, or uninsured pregnant women who have no access to prenatal care during any stage of pregnancy and the behaviors and lifestyles that pose a risk to the health of the mother and fetus contribute to the problem (U.S. Department of Health and Human Services, 2000).

Care of these high risk patients requires the unified efforts of medical and nursing personnel. The high risk patient and the factors associated with a diagnosis of high risk are identified in this chapter; diagnostic techniques used to monitor the maternal-fetal unit are emphasized.

DEFINITION AND SCOPE OF THE PROBLEM

A high risk pregnancy is one in which the life or health of the mother or fetus is jeopardized by a disorder coincidental with or unique to pregnancy. For the mother the high risk status arbitrarily extends through the puerperium (30 days after childbirth). Postbirth maternal complications are usually resolved within 1 month of birth, but perinatal morbidity may continue for months or years.

High risk pregnancy represents a critical problem of modern medical and nursing care. The new social emphasis on the quality of life and the wanted child has resulted in a reduction of family size and the number of unwanted pregnancies. At the same time, technologic advances have enabled pregnancies in previously infertile couples. As a consequence, emphasis is on the safe birth of normal infants who can develop to their potential. Scientific and technologic advances have allowed perinatal health care to reach a level far beyond that previously available.

Although pregnancy is often referred to as a maturational crisis, the diagnosis of high risk imposes another crisis, a situational one (e.g., loss of pregnancy before the anticipated date; development of gestational diabetes mellitus with its potential complications; birth of a neonate who does not meet cultural, societal, or familial norms and expectations).

MATERNAL HEALTH PROBLEMS

The leading causes of maternal death attributable to pregnancy differ over the world. In general, three major causes have persisted for the last 40 years: hypertensive disorders, infection, and hemorrhage (National Center for Health Statistics, 1997). Factors that are strongly related to maternal death include age (less than 20 years and 35 years or greater), lack of prenatal care, low educational attainment, unmarried status, and nonwhite race. African-American maternal mortality rates are more than three times higher than those for Caucasian women (Murphy, 2000). In the United States, the maternal death rate remained between 7 and 8 per 100,000 live births in the 1990s; however, the goal set by Healthy People 2010 is no more than 3.3 maternal deaths per 100,000 live births (Guyer et al., 2000; U.S. Department of Health and Human Services, 2000). Reaching this goal will be a significant challenge.

Although the overall number of maternal deaths is small, maternal mortality remains a significant problem because a high proportion of deaths are preventable, primarily through improving the access to and use of prenatal care services. Nurses can be instrumental in educating the public about the importance of obtaining early and regular care during pregnancy.

 

FETAL AND NEONATAL HEALTH PROBLEMS

The leading causes of death in the neonatal period are congenital anomalies, disorders related to preterm birth and low birth weight, sudden infant death syndrome, respiratory distress syndrome, and the effects of maternal complications (National Center for Health Statistics, 1998). Increased rates of survival during the neonatal period have resulted largely from high quality prenatal care and the improvement in perinatal services, including technologic advances in neonatal intensive care and obstetrics. Perinatal services must be modified to meet contemporary health care needs.

 

REGIONALIZATION OF HEALTH CARE SERVICES

Early and ongoing risk assessment is a crucial component of perinatal care. Conditions associated with perinatal morbidity and mortality can be prevented, treated, or referred to more skilled health care providers. Factors to consider when determining a patient's risk status include resources available locally to treat the condition, availability of appropriate facilities for transport if needed, and determination of the best match for the patient's needs.

Not all facilities develop and maintain the full spectrum of services required for high risk perinatal patients. As a consequence, the concept of regionalization of health care services—facilities within a geographic region organized to provide different levels of care—emerged.

In ambulatory settings, providers must distinguish themselves by the level of care they provide. Basic care is provided by obstetricians, family physicians, certified nurse-midwives, and other advanced practice clinicians approved by local governance. Routine risk-oriented prenatal care, education, and support is provided. Providers offering specialty care are obstetricians who provide fetal diagnostic testing and management of obstetric and medical complications in addition to basic care. Subspecialty care is provided by maternal-fetal medicine specialists and includes the aforementioned in addition to genetic testing, advanced fetal therapies, and management of severe maternal and fetal complications (American Academy of Pediatrics/American College of Obstetricians and Gynecologists [AAP/ACOG], 1997).

In hospital settings, perinatal services are also designated as basic, specialty, or subspecialty. Criteria for basic perinatal services include care of all women admitted to the service, with an established triage system for high risk patients who should be transferred to a higher level of care; ability to perform a cesarean birth within 30 minutes of a decision to do so; availability of blood and blood products; availability of radiology, anesthesia, and laboratory services on a 24-hour basis; presence of nursery and postpartum care; resuscitation and stabilization of all neonates born in the hospital; availability of transport for all sick neonates; family visitation; and data collection and retrieval (AAP/ACOG, 1997).

Specialty hospital care includes the aforementioned requirements in addition to care of high risk mothers and fetuses, stabilization of ill neonates before transfer, and care of preterm infants with a birth weight of 1500 g or more. Preterm labor or impending births of 32 weeks of gestation or less should be transferred for subspecialty care. Other criteria for subspecialty care include comprehensive prenatal services, research and educational support, and utilization of high risk technologies. Collaboration among providers to meet the patient's needs is key in reducing perinatal morbidity and mortality rates (AAP/ACOG, 1997).

Assessment for Risk Factors

In the past, risk factors were evaluated only from a medical viewpoint; thus only adverse medical, obstetric, or physiologic conditions were considered to place the patient at risk. Today, a more comprehensive approach to high risk pregnancy is used, and the factors associated with high risk childbearing are grouped into broad categories based on threats to health and pregnancy outcome. Categories of risk include biophysical, psychosocial, sociodemographic, and environmental (Gilbert & Harmon, 1998) (Box 1).

Box 1 Categories of High Risk Factors BIOPHYSICAL FACTORS 1. Genetic considerations. Genetic factors may interfere with normal fetal or neonatal development, result in congenital anomalies, or create difficulties for the mother. These factors include defective genes, transmissible inherited disorders and chromosome anomalies, multiple pregnancy, large fetal size, and ABO incompatibility. 2. Nutritional status. Adequate nutrition, without which fetal growth and development cannot proceed normally, is one of the most important determinants of pregnancy outcome. Conditions that influence nutritional status include young age; three pregnancies in the previous 2 years; tobacco, alcohol, or drug use; inadequate dietary intake because of chronic illness or food fads; inadequate or excessive weight gain; and hematocrit value less than 33%. 3. Medical and obstetric disorders. Complications of current and past pregnancies, obstetric-related illnesses, and pregnancy losses put the patient at risk (see Box 2). PSYCHOSOCIAL FACTORS 1. Smoking. A strong, consistent, causal relationship has been established between maternal smoking and reduced birth weight. Risks include low-birth-weight infants, higher neonatal mortality rates, increased miscarriages, and increased incidence of premature rupture of membranes. These risks are aggravated by low socioeconomic status, poor nutritional status, and concurrent use of alcohol. 2. Caffeine. Birth defects in humans have not been related to caffeine consumption. High intake (three or more cups of coffee per day) has been related to a slight decrease in birth weight. 3. Alcohol. Although its exact effects in pregnancy have not been quantified and its mode of action is largely unexplained, alcohol exerts adverse effects on the fetus, resulting in fetal alcohol syndrome, fetal alcohol effects, learning disabilities, and hyperactivity. 4. Drugs. The developing fetus may be adversely affected by drugs through several mechanisms. They can be teratogenic, cause metabolic disturbances, produce chemical effects, or cause depression or alteration of central nervous system function. This category includes medications prescribed by a health care provider or bought over the counter, herbs, and commonly abused drugs such as heroin, cocaine, and marijuana. 5. Psychologic status. Childbearing triggers profound and complex physiologic, psychologic, and social changes, with evidence to suggest a relationship between emotional distress and birth complications. This risk factor includes conditions such as specific intrapsychic disturbances and addictive lifestyles; a history of child or intimate partner abuse; inadequate support systems; family disruption or dissolution; maternal role changes or conflicts; noncompliance with cultural norms; unsafe cultural, ethnic, or religious practices; and situational crises. SOCIODEMOGRAPHIC FACTORS 1. Low income. Poverty underlies many other risk factors and leads to inadequate financial resources for food and prenatal care, poor general health, increased risk of medical complications of pregnancy, and greater prevalence of adverse environmental influences. 2. Lack of prenatal care. Failure to diagnose and treat complications early is a major risk factor arising from financial barriers or lack of access to care; depersonalization of the system, resulting in long waits, routine visits, variability in health care personnel, and unpleasant physical surroundings; lack of understanding of the need for early and continued care or cultural beliefs that do not support this need; and fear of the health care system and its providers. 3. Age. Women at both ends of the childbearing age spectrum have a higher incidence of poor outcomes; however, age may not be a risk factor in all cases. Both physiologic and psychologic risks should be evaluated. Adolescents —More complications are seen in young mothers (younger than 15 years old), who have a 60% higher mortality rate than those older than age 20, and in pregnancies occurring less than 3 years after menarche. Complications include anemia, pregnancy-induced hypertension (PIH), prolonged labor, and contracted pelvis and cephalopelvic disproportion. Long-term social implications of early motherhood are lower educational status, lower income, increased dependence on government support programs, higher divorce rates, and higher parity. Mature mothers—The risks to older mothers are not  from age alone but from other considerations such as number and spacing of previous pregnancies; genetic disposition of the parents; and medical history, lifestyle, nutrition, and prenatal care. The increased likelihood of chronic diseases and complications that arise from more invasive medical management of a pregnancy and labor combined with demographic characteristics put an older woman at risk. Medical conditions more likely to be experienced by mature women include hypertension and PIH, diabetes, extended labor, cesarean birth, placenta previa, abruption placentae, and mortality. Her fetus is at greater risk for low birth weight or macrosomia, chromosomal abnormalities, congenital malformations, and neonatal mortality. 4. Parity. The number of previous pregnancies is a risk factor that is associated with age and includes all first pregnancies, especially a first pregnancy at either end of the childbearing-age continuum. The incidence of PIH and dystocia is higher with a first birth. 5. Marital status. The increased mortality and morbidity rates for unmarried women, including a greater risk for PIH, are often related to inadequate prenatal care and a younger childbearing age. 6. Residence. The availability and quality of prenatal care varies widely with geographic residence. Women in metropolitan areas have more prenatal visits than those in rural areas, who have fewer opportunities for specialized care and consequently a higher incidence of maternal mortality. Health care in the inner city where residents are usually poorer and begin childbearing earlier and continue longer, may be of lower quality than in a more affluent neighborhood. 7. Ethnicity. Although ethnicity itself is not a major risk factor, race is an indicator of other sociodemographic risk factors. Nonwhite women are more than three times as likely as Caucasian women to die of pregnancy-related causes. African-American babies have the highest rates of prematurity and low birth weight, with the infant mortality rate among African-Americans being more than double that for Caucasians. ENVIRONMENTAL FACTORS Various environmental substances can affect fertility and fetal development, the chance of a live birth, and the child's subsequent mental and physical development. Environmental influences include infections; radiation; chemicals such as pesticides, therapeutic drugs, illicit drugs, industrial pollutants, cigarette smoke; stress; and diet. Paternal exposure to mutagenic agents in the workplace has been associated with an increased risk of miscarriage.

 

Biophysical risks include factors that originate within the mother or fetus and affect the development or functioning of either one or both. Psychosocial risks are maternal behaviors and adverse lifestyles that have a negative effect on the health of the mother or fetus. These risks may include emotional distress and disturbed interpersonal relationships, as well as inadequate social support and unsafe cultural practices. Sociodemographic risks arise from the mother and her family. These risks may place the mother and fetus at risk. Environmental factors include hazards in the workplace and the woman's general environment. Risk factors are interrelated and cumulative in their effects. Box 2 lists specific pregnancy problems and risk factors; risk factors of the postpartum woman and newborn are shown in Box 3.

 

Box 2Specific Pregnancy Problems and Related Risk Factors PRETERM LABOR Age younger than 16 or older than 35 years Low socioeconomic status Maternal weight below 50 kg Poor nutrition Previous preterm birth Incompetent cervix Uterine anomalies Smoking Drug addiction and alcohol abuse Pyelonephritis, pneumonia Multiple gestation Anemia Abnormal fetal presentation Preterm rupture of membranes Placental abnormalities Infection Abdominal surgery in current pregnancy History of cervical surgery POLYHYDRAMNIOS Diabetes mellitus Multiple gestation Fetal congenital anomalies Isoimmunization (Rh or ABO) Nonimmune hydrops Abnormal fetal presentation INTRAUTERINE GROWTH RESTRICTION (IUGR) Multiple gestation Poor nutrition Maternal cyanotic heart disease Prior pregnancy with IUGR Maternal collagen diseases Chronic hypertension Pregnancy-induced hypertension Recurrent antepartum hemorrhage Smoking Maternal diabetes with vascular problems Fetal infections Fetal cardiovascular anomalies Drug addiction and alcohol abuse Fetal congenital anomalies Hemoglobinopathies OLIGOHYDRAMNIOS Renal agenesis (Potter syndrome) Prolonged rupture of membranes IUGR Intrauterine fetal death POSTTERM PREGNANCY Anencephaly Placental sulfatase deficiency Perinatal hypoxia, acidosis Placental insufficiency CHROMOSOMAL ABNORMALITIES Maternal age 35 years or older Balanced translocation (maternal and paternal)

 

Box 3 Factors That Place the Postpartum Woman and Neonate at High Risk MOTHER Hemorrhage Infection Abnormal vital signs Traumatic labor or birth Psychosocial factors INFANT (For admission to NICU) High Risk Infants who continue with or develop signs of respiratory distress syndrome or other respiratory distress Asphyxiated infants (Apgar score less than 6 at 5 min), resuscitation required at birth Preterm infants, dysmature infants Infants with cyanosis or suspected cardiovascular disease, persistent cyanosis Infants with major congenital malformations requiring surgery, chromosomal anomalies Infants with convulsions, sepsis, hemorrhagic diathesis, or shock Meconium aspiration syndrome CNS depression for more than 24 hr Hypoglycemia Hypocalcemia Hyperbilirubinemia Moderate Risk Dysmaturity Prematurity (weight between 2000 and 2500 g) Apgar score less than 5 at 1 min Feeding problems Multifetal birth Transient tachypnea Hypomagnesemia or hypermagnesemia Hypoparathyroidism Failure to gain weight Jitteriness or hyperactivity Cardiac anomalies not requiring immediate catheterization Heart murmur Anemia CNS depression for less than 24 hr

 

ANTEPARTUM TESTING/BIOPHYSICAL ASSESSMENT

The major expected outcome of antepartum testing is the detection of potential fetal compromise. Ideally, the technique used identifies fetal compromise before intrauterine asphyxia of the fetus so that the health care provider can take measures to prevent or minimize adverse perinatal outcomes. No single test can provide this information. Assessment tests should be selected based on their effectiveness, and the results must be interpreted in light of the complete clinical picture. The most reliable evidence for effectiveness is provided by randomized controlled trials (ACOG, 1999). Nurses can be informed about the most recent research on fetal assessment by using an up-to-date systematic review such as the Cochrane Database of Systematic Reviews (Enkin et al., 1995). Table 1 lists evidence for recommending care for fetal assessment screening based on this database.

 

Table 1 Fetal Assessment Screening: Recommendations for Care
FETAL ASSESSMENT TEST	RECOMMENDATION/CONCLUSION
Doppler ultrasound use in pregnancy at high risk for fetal compromise	Beneficial effects
Ultrasound use to estimate gestational age in first and early second trimesters	Effects likely to be beneficial
Ultrasound use to confirm multiple pregnancy
Ultrasound use for placental location in placenta previa
Early second trimester amniocentesis for identification of chromosomal
abnormalities
Formal systems of risk scoring	There is a trade-off between beneficial and adverse effects
Routine use of early ultrasound
CVS versus amniocentesis for diagnosing chromosomal abnormalities
Serum alpha-fetoprotein screening for neural tube defects
Routine fetal movement counts to improve perinatal outcome
Placental grading by ultrasound to improve perinatal outcome	Unknown effectiveness
Biophysical profile for fetal surveillance
Routine use of ultrasound for fetal anthropometry (body measurements) in late pregnancy	Unlikely to be beneficial
Use of Doppler ultrasound in all pregnancies
Measurement of placental hormones (estriol)
Nipple stimulation test to improve perinatal outcome	Likely to be ineffective or harmful
Nonstress test to improve perinatal outcome
Contraction stress test to improve perinatal outcome

 

DAILY FETAL MOVEMENT COUNT

Assessment of fetal activity by the mother is a simple yet valuable method for monitoring the condition of the fetus. The daily fetal movement count (DFMC), also known as the "kick count," can be done at home, is noninvasive, is simple to understand, and usually does not interfere with a daily routine. The presence of movements is generally a reassuring sign of fetal health. The DFMC can be used in determining the need for more precise fetal surveillance tests (Christensen & Rayburn, 1999).

Several protocols are used for counting. Except for establishing a very low number of daily fetal movements or a trend toward decreased motion, the clinical value of the absolute number of fetal movements has not been established, except in the situation in which fetal movements cease entirely for 12 hours (the fetal alarm signal). Generally, a count of less than three fetal movements within 1 hour warrants further evaluation by nonstress or contraction stress testing, biophysical profile, or a combination of these. Patients should be taught the significance of fetal movements, the procedure for counting that is to be used, and how to record findings on a daily fetal movement record.

 

NURSE ALERT In assessing fetal movements it is important to remember that they are usually not present during the fetal sleep cycle; they may be temporarily reduced if the woman is taking depressant medications, drinking alcohol, or smoking a cigarette; and they do not decrease as the woman nears term.

 

ULTRASONOGRAPHY

Ultrasound can be done abdominally or transvaginally during pregnancy. Both produce a three-dimensional view from which a pictorial image is obtained. Abdominal ultrasonography is more useful after the first trimester when the pregnant uterus becomes an abdominal organ. For the procedure the woman may need to have a full bladder to get a better image of the fetus. Transmission gel or paste is applied to the abdomen before a transducer is moved over the skin to enhance transmission and reception of the sound waves.

Transvaginal ultrasonography, in which the lubricated probe is inserted into the vagina, allows pelvic anatomy to be evaluated in greater detail and intrauterine pregnancy to be diagnosed earlier (Cunningham et al., 2001). A transvaginal ultrasound examination is well tolerated by most patients because it alleviates the need for a full bladder. It is especially useful in obese women whose thick abdominal layers cannot be penetrated adequately by an abdominal approach. Transvaginal ultrasonography is optimally used in the first trimester to detect ectopic pregnancies, monitor the developing embryo, help identify abnormalities, and help establish gestational age. In some instances, it may be used as an adjunct to abdominal scanning to evaluate preterm labor in second- and third-trimester pregnancies (Guzman et al., 1998).

 

Indications for use

During the first trimester, ultrasound examination is performed to obtain information on (1) number, size, and location of gestational sacs, (2) presence or absence of fetal cardiac and body movements, (3) presence or absence of uterine abnormalities (e.g., bicornuate uterus, fibroids) or adnexal masses (e.g., ovarian cysts, an ectopic pregnancy), (4) date of pregnancy (by measuring the crownrump length), and (5) presence and location of an intrauterine contraceptive device.

During the second and third trimesters, information on the following conditions is sought: (1) fetal viability, number, position, gestational age, growth pattern, and anomalies; (2) amniotic fluid volume; (3) placental location and maturity; (4) uterine fibroids and anomalies; (5) adnexal masses; and (6) cervical length.

 

Findings

Ultrasonography can lead to earlier diagnoses, allowing therapy to be instituted early in the pregnancy and thereby decrease the severity and duration of morbidity, both physical and emotional, for the family.

Fetal heart activity. Fetal heart activity can be demonstrated as early as 6 to 7 weeks by real-time echo scanners and at 10 to 12 weeks by Doppler mode. By 9 to 10 weeks, gestational trophoblastic disease can be diagnosed. Fetal death can be confirmed by lack of heart motion, the presence of fetal scalp edema, and maceration and overlap of the cranial bones.

Gestational age. Gestational dating by ultrasonography is indicated for conditions such as (1) uncertain dates for the last normal menstrual period, (2) recent discontinuation of oral contraceptives, (3) bleeding episode during the first trimester, (4) uterine size that does not agree with dates, and (5) other high risk conditions.

During the first 20 weeks of gestation, ultrasonography provides an accurate assessment of gestational age because most normal fetuses grow at the same rate. Accuracy is increased as the fetus ages because more than one variable is measured. The four methods of fetal age estimation are (1) determination of gestational sac dimensions (at approximately 8 weeks), (2) measurement of crown-rump length (between 7 and 14 weeks), (3) measurement of the biparietal diameter (BPD) (after 12 weeks), and (4) measurement of femur length (after 12 weeks). Fetal BPD at 36 weeks should be approximately 8.7 cm. Term pregnancy and fetal maturity can be diagnosed with some confidence if the biparietal measurement by ultrasound examination is greater than 9.8 cm (Fig. 1), especially when this is combined with appropriate femur length measurement.

 

 

Fig. 1 Real-time image of fetal biparietal diameters at 18 weeks. (From Athey, P., & Hadlock, F. [1985]. Ultrasound in obstetrics and gynecology [2nd ed.]. St. Louis: Mosby.)

 

In later gestational periods, serial measurements can provide a more accurate determination of fetal age. Two and preferably three composite measurements are recommended, at least 2 weeks apart, and these are plotted against standard fetal growth curves. This method, when applied between 24 and 32 weeks of gestation, yields an estimation error of 10 days more or less than the actual age (Manning, 1999b).

Fetal growth. Fetal growth is determined by both intrinsic growth potential and environmental factors. Conditions that require ultrasound assessment of fetal growth include (1) poor maternal weight gain or pattern of weight gain, (2) intrauterine growth restriction (IUGR) in a previous pregnancy, (3) chronic infections, (4) ingestion of drugs (tobacco, alcohol, over-the-counter, and street drugs), (5) maternal diabetes mellitus, (6) hypertension, (7) multifetal pregnancy, and (8) other medical or surgical complications.

Serial evaluations of BPD and limb length can differentiate between size discrepancy resulting from inaccurate dates and true IUGR. IUGR may be symmetric (the fetus being small in all parameters) or asymmetric (head and body growth varying). Symmetric IUGR reflects a chronic or long-standing insult and may be caused by low genetic growth potential, intrauterine infection, undernutrition, heavy smoking, or chromosomal aberration. Asymmetric growth suggests an acute or late-occurring deprivation, such as placental insufficiency resulting from hypertension, renal disease, or cardiovascular disease.

Macrosomic infants (those weighing more than 4000 g) are at increased risk for trauma during birth. In addition, fetal macrosomia associated with maternal glucose intolerance carries an increased risk of intrauterine fetal death.

Fetal anatomy and presentation. Anatomic structures that may be identified by ultrasonography (depending on the gestational age) include the following: head (including ventricles and blood vessels) (Fig. 2, A), neck, spine, heart, stomach, small bowel, liver, kidneys, bladder, and limbs. Ultrasonography permits the confirmation of normal anatomy, as well as the detection of major fetal malformations. The presence of an anomaly may influence the location of birth (e.g., a delivery room versus a labor-delivery-recovery room or a subspecialty center versus a basic care center) and the method of birth to optimize neonatal outcomes. The number of fetuses and their presentations may also be assessed by ultrasonography, allowing plans for therapy and mode of birth to be made in advance.

 

Fig. 2 Two views of the fetus during ultrasonography. A, Fetal face (20 weeks). B, Umbilical cord (26 weeks). (Courtesy Advanced Technology Laboratories, Bothell, WA.)

 

Fetal genetic disorders and physical anomalies. Fetal nuchal translucency (FNT), a new prenatal screening technique, uses ultrasound measurement of fluid in the nape of the fetal neck between 10 and 14 weeks of gestation to identify possible fetal abnormalities. A finding of abnormal fluid collection that is greater than 2.5 mm is considered abnormal, and a measurement of 3 mm or greater is highly indicative of genetic disorders, physical anomalies, or both. If the FNT is abnormal, diagnostic genetic testing is recommended (Beamer, 2001).

Placental position and function. The pattern of uterine and placental growth and the fullness of the maternal bladder influence the apparent location of the placenta by ultrasonography. During the first trimester, differentiation between the endometrium and a small placenta is difficult. By 14 to 16 weeks the placenta is clearly defined, but if it is seen to be low lying, its relationship to the internal cervical os can sometimes be dramatically altered by varying the fullness of the maternal bladder. In approximately 15% to 2O°/o of all pregnancies in which ultrasound scanning is performed during the second trimester, the placenta seems to be overlying the os, but the incidence of placenta previa at term is only 0.5%. Thus the diagnosis of placenta previa can seldom be confirmed before 27 weeks. Another use for ultrasonography is grading of placental maturation (Box 4). Calcium deposits are of significance in postterm pregnancies because as they increase, the available surface area that can be adequately bathed by maternal blood decreases. The point at which this results in fetal wastage and hypoxia cannot be determined precisely; however, the effects are usually observable by 42 weeks and are progressive (Gilbert & Harmon, 1998).

 

Box 4 Placental Grading Third-trimester grading of placental maturation can be accomplished by ultrasound scanning. The placenta undergoes detectable maturational changes throughout gestation; a relationship has been noted between advancing placental grade and fetal pulmonary maturity. Placentas are graded as 0,1, II, and III (with grade III placentas being the most mature) on the basis of the identification and distribution of calcium deposits within the fetal portion (Manning, 1999b). Ultrasound examination can identify changes in the chorionic plate, placental substance, and basal layer of the placenta that correspond to the various grades: (1) grade 0 placentas are seen in the first and second trimesters, (2) grade I placentas appear between 30 and 32 weeks and may even persist until term, (3) grade II placentas are observed at around 36 weeks and persist until term in 45% of pregnancies, and (4) grade III placentas are seen at 38 weeks and reflect the greatest maturation. However, only a small number of placentas are grade III.

 

Adjunct to amniocentesis, percutaneous umbilical blood sampling, and chorionic villus sampling. The safety of amniocentesis is increased when the positions of the fetus, placenta, and pockets of amniotic fluid can be identified accurately. Ultrasound scanning has reduced risks previously associated with amniocentesis, such as fetomaternal hemorrhage from a pierced placenta. Percutaneous umbilical blood sampling and chorionic villus sampling are also guided by ultrasonography to identify the cord and chorion frondosum accurately (see Fig. 2, B).

Fetal well-being

Physiologic parameters of the fetus that can be assessed with ultrasound scanning include amniotic fluid volume, vascular waveforms from the fetal circulation, heart motion, fetal breathing movements, fetal urine production, and fetal limb and head movements. Assessment of these parameters, singly or in combination, yields a fairly reliable picture of fetal well-being. The significance of these findings is discussed in the following sections.

Amniotic fluid volume. Abnormalities of amniotic fluid volume (AFV) are often associated with fetal disorders. Subjective determinants of oligohydramnios (decreased fluid) include the absence of fluid pockets in the uterine cavity and the impression of crowding of small fetal parts. An objective criterion of decreased AFV is met if the largest pocket of fluid measured in two perpendicular planes is less than 2 cm. In the case of polyhydramnios (increased fluid), subjective criteria include multiple large pockets of fluid (greater than 12 cm in the vertical axis), the impression of a floating fetus, and free movement of fetal limbs (Manning, 1999a). The total AFV can be evaluated by a method developed in which the depths (in centimeters) of the amniotic fluid in all four quadrants surrounding the maternal umbilicus are totaled, providing an amniotic fluid index (AFI). An AFI is normal if the summed value is more than 80 cm and less than 180 cm (Manning, 1999a).

Oligohydramnios is associated with congenital anomalies (such as renal agenesis), growth restriction, and fetal distress during labor. Polyhydramnios is associated with neural tube defects, obstruction of the fetal gastrointestinal tract, multiple fetuses, and fetal hydrops.

Doppler blood flow analysis. One of the major advances in perinatal medicine is the ability to study blood flow noninvasively in the fetus and placenta. Doppler blood flow analysis through the use of ultrasound is a helpful adjunct in the management of pregnancies at risk because of hypertension, IUGR, diabetes mellitus, multiple fetuses, or preterm labor (Miller, 1998). The velocity of the red blood cells (RBCs) can be determined by measuring the change in the frequency of the sound wave reflected off the cells.

Velocity waveforms from umbilical and uterine arteries, reported as systolic-to-diastolic (S/D) ratios, can be first detected at 15 weeks of pregnancy (Fig. 3). Because of the progressive decline in resistance in both the umbilical and uterine arteries, this ratio decreases as pregnancy advances. Most fetuses will achieve an S/D ratio of 3 or less by 30 weeks. Persistent elevation of S/D ratios after 30 weeks is associated with IUGR, usually resulting from uteroplacental insufficiency. In postterm pregnancies, an elevated S/D ratio indicates a poorly perfused placenta. Abnormal results are also seen with certain chromosome abnormalities (trisomy 13 and 18) in the fetus and with lupus erythematosus in the mother. Exposure to nicotine from maternal smoking has also been reported to increase the S/D ratio.

 

Fig. 3 Normal and abnormal uteroplacental vessels at 34 weeks. A, Normal S/D ratio of 2.2. B, S/D ratio of 3.4. (From Schulman, H. [1990]. Doppler ultrasound. In R. Eden & F. Boehm [Eds.], Assessment and care of the fetus: Physiological, clinical, and medicolegal principles. Norwalk, CT: Appleton & Lange.)

 

Biophysical profile. Real-time ultrasound permits detailed assessment of the physical and physiologic characteristics of the developing fetus and cataloging of normal and abnormal biophysical responses to stimuli. The biophysical profile (BPP) is a noninvasive dynamic assessment of a fetus and its environment by ultrasonography and external fetal monitoring.

BPP scoring is a method of fetal risk surveillance based on the assessment of both acute and chronic markers of nonreassuring fetal status. The BPP includes fetal breathing movements, fetal movements, fetal tone, fetal heart rate patterns by means of a nonstress test, and AFV; the procedure may therefore be considered a physical examination of the fetus, including determination of vital signs.

The fetal response to central hypoxia is alteration in movement, muscle tone, breathing, and heart rate patterns. The presence of normal fetal biophysical activities indicates that the central nervous system (CNS) is functional and the fetus therefore is not hypoxemic (Manning, 1999a). BPP variables and scoring are detailed in Table 2.

 

TABLE 2 BIOPHYSICAL PROFILE
VARIABLES	NORMAL (SCORE = 2)		ABNORMAL (SCORE = O)
Fetal breathing movements	One or more episodes in 30 min, each lasting a30 sec		Episodes absent or no episode 30 sec in 30 min
Gross body movements	Three or more discrete body or limb movements in 30 min (episodes of active continuous movement being considered as a single movement)		Less than three episodes of body or limb movements in 30 min
Fetal tone	One or more episodes of active extension with return to flexion of fetal limb(s) or trunk, opening andclosing of hand being considered normal tone		Slow extension with return to flexion, movement of limb in full extension. or fetal movement absent
Reactive fetal heart rate	Two or more episodes of acceleration (2=15 beats/min) in 20 min, each lasting >15 sec and associated with fetal movement		Less than two episodes of acceleration or acceleration of <15 beats/min in 20 min
Qualitative amniotic fluid volume	One or more pockets of fluid measuring s1 cm in two perpendicular planes		Pockets absent or pocket <1 cm in two perpendicular planes
SCORE
Normal	8-10 (if amniotic fluid index is adequate)
Equivocal	6
Abnormal	<4

 

 

The BPP is an accurate indicator of impending fetal death. Fetal acidosis can be diagnosed early with a nonreactive nonstress test and absent fetal breathing movements. An abnormal BPP score and oligohydramnios are indications that labor should be induced (Manning, 1999a). Fetal infection in women whose membranes rupture prematurely (at less than 37 weeks of gestation) can be diagnosed early by changes in biophysical activity that precede the clinical signs of infection and indicate the  necessity for immediate birth. When the BPP score is normal and the risk of fetal death low, intervention is indicated only for obstetric or maternal factors.

 

Nursing role

Although a growing number of nurses perform ultrasound scans and BPPs in certain centers, the main role of nurses is in counseling and educating women about the procedure.

 

LEGAL TIP Performance of Limited Ultrasound Examinations

Nurses who have the training and competence may perform limited ultrasound examinations if it is within the scope of practice in their state or area and consistent with regulations of the agencies in which they practice (Treanor, 1998). Limited ultrasound examinations include identification of fetal number, fetal presentation, fetal cardiac activity, location of the placenta, and BPP, including amniotic fluid volume assessment. Patients should be informed about the limited information provided by these examinations. They are not meant to evaluate or identify fetal anomalies, assess fetal age, or estimate fetal weight. The obstetric health care provider is responsible for obtaining a more comprehensive ultrasound examination when complete patient assessment is necessary (Association of Women's Health, Obstetric and Neonatal Nurses, 1998).

 

For an abdominal ultrasound the woman is positioned comfortably with small pillows under her head and knees. The display panel is positioned so that the woman and her partner can observe the images on the screen if they desire. A transvaginal ultrasound may be performed with the woman in a lithotomy position or with her pelvis elevated by towels, cushions, or a folded pillow. This tilt is optimal to image the pelvic structures. A protective cover such as a condom, the finger of a clean rubber surgical glove, or a special probe cover provided by the manufacturer is used to cover the transducer probe. The probe is lubricated with a water-soluble gel and placed in the vagina either by the examiner or by the woman herself. During the examination the position of the probe or the tilt of the examining table may be changed so that the complete pelvis is in view. The procedure is not physically painful, although the woman will feel pressure as the probe is moved.

 

MAGNETIC RESONANCE IMAGING

Magnetic resonance imaging (MRI) can evaluate (1) fetal structure (e.g., CNS, thorax, abdomen, genitourinary tract, musculoskeletal system) and overall growth; (2) placenta (e.g., position, density, presence of gestational trophoblastic disease); (3) quantity of amniotic fluid; (4) maternal structures (uterus, cervix, adnexa, and pelvis); (5) biochemical status (e.g., pH, adenosine triphosphate content) of tissues and organs; and (6) soft tissue and functional anomalies.

The woman is placed in the supine position on a table that is slid into the bore of the main magnet, which is similar in appearance to a computed tomography scanner. Depending on the reason for the study, the procedure may take from 20 to 60 minutes, during which time the woman must be perfectly still except for short respites. Because of the long time needed to produce magnetic resonance images, the fetus will probably move, which will obscure anatomic details. The only way to ensure that this does not occur is to administer a sedative to the mother, but this approach should be reserved for selected cases in which visualization of fetal detail is critical. MRI has little effect on the fetus; concerns that the fetal heart rate or fetal movement would decrease have not been supported (Poutamo et al., 1998).

BIOCHEMICAL ASSESSMENT

Biochemical assessment involves biologic examination (e.g., chromosomes in exfoliated cells) and chemical determinations (e.g., lecithin-to-sphingomyelin [L/S] ratio and bilirubin level) (Table 3). Procedures used to obtain the needed specimens include amniocentesis, percutaneous umbilical blood sampling, chorionic villus sampling, and maternal blood sampling (Box 5).

 

Table 3 Summary of Biochemical Monitoring Techniques
TEST	POSSIBLE FINDING	CLINICAL SIGNIFICANCE
MATERNAL BLOOD
Coombs' test
AFP
AMNIOTIC FLUID ANALYSIS
Color	Meconium
Lung profile        L/S ratio        Phosphatidylglycerol	>2 Present
Creatinine	>2 mg/dl	Gestational age >36 wk
Bilirubin (AOD 450/nm)	<0.015     High levels	Gestational age >36 wk, normal pregnancy Fetal hemolytic disease in Rh isoimmunized pregnancies
Lipid cells	>10%	Gestational age >35 wk
AFP	High levels after 15-wk gestation	Open neural tube or other defect
Osmolality	Decline after 20-wk gestation	Advancing gestational age
Genetic disorders Sex-linked           Chromosomal           Metabolic	Dependent on cultured cells for karyotype and enzymatic activity	Counseling possibly required

 

Box 5 Fetal Rights Amniocentesis, PUBS, and CVS are prenatal tests used for diagnosing fetal defects in pregnancy. They are invasive and carry risks to the mother and fetus. A consideration of abortion is linked to the performance of these tests because there is no treatment for genetically affected fetuses. Thus the issue of fetal rights is a key ethical concern in prenatal testing for fetal defects.

 

AMNIOCENTESIS

Amniocentesis is performed to obtain amniotic fluid, which contains fetal cells. Under direct ultrasonographic visualization, a needle is inserted transabdominally into the uterus, amniotic fluid is withdrawn into a syringe, and the various assessments are performed (see Table 3). Amniocentesis is possible after week 14 of pregnancy, when the uterus becomes an abdominal organ and sufficient amniotic fluid is available for testing (Fig. 4). Indications for the procedure include prenatal diagnosis of genetic disorders or congenital anomalies (neural tube defects in particular), assessment of pulmonary maturity, and diagnosis of fetal hemolytic disease.

 

Fig. 4 A, Amniocentesis and laboratory use of amniotic fluid aspirant. B, Transabdominal amniocentesis. (B, Courtesy Marjorie Pyle, RNC, Lifecircle, Costa Mesa, CA.)

 

Complications in the mother and fetus occur in fewer than 1% of cases and include the following:

Maternal-hemorrhage, fetomaternal hemorrhage with possible maternal Rh isoimmunization, infection, labor, abruptio placentae, inadvertent damage to the intestines or bladder, and amniotic fluid embolism. Because of the possibility of fetomaternal hemorrhage, it is standard practice after an amniocentesis to administer Rh0 D immune globulin (RhoGAM) to the woman who is Rh negative.

Fetal— leakage of amniotic fluid, hemorrhage, infection (amnionitis), direct injury from the needle, miscarriage or preterm labor, and death. Many of the complications have been minimized or eliminated by using ultrasonography to direct the procedure.

 

Genetic problems

Prenatal assessment of genetic disorders is indicated in women more than 35 years old, with a previous child with a chromosomal abnormality, or with a family history of chromosomal anomalies. Inherited errors of metabolism (such as Tay-Sachs disease, hemophilia, and thalassemia) and other disorders for which marker genes are known may also be detected. Cells are cultured for karyotyping of chromosomes (see Chapter 7). Karyotyping also permits determination of fetal sex, which is important if a sexlmked disorder is suspected.

Alpha-fetoprotein (AFP) levels are assessed as a followup for elevated levels in maternal serum. High AFP levels in amniotic fluid help confirm the diagnosis of a neural tube defect such as spina bifida or anencephaly or an abdominal wall defect such as omphalocele. AFP levels may also be elevated in a normal multifetal pregnancy and with intestinal atresia, presumably caused by lack of fetal swallowing.

 

Fetal maturity

Accurate assessment of fetal maturity is possible through examination of amniotic fluid or its exfoliated cellular contents. Laboratory tests that are determinants of term pregnancy and fetal maturity are described in Table 4.

 

Table 4 Interpretation of the Nonstress Test
RESULT	INTERPRETATION	CLINICAL SIGNIFICANCE
Reactive	Two or more accelerations of FHR of 15 beats/min lasting 15 sec or more, associated with each fetal movement in a 20 min period (see Fig. 7)	As long as twice-weekly NSTs remain reactive, most high risk pregnancies are allowed to continue
Nonreactive	Any tracing with either no FHR accelerations or accelerations <15 beats/min or lasting less than 15 sec throughout any fetal movement during testing period	Further indirect monitoring may be attempted with abdominal fetal electrocardiography in an effort to clarify FHR pattern and quantitate variability; external monitoring should continue, and CST or BPP should be done
Unsatisfactory	Quality of FHR recording not adequate for interpretation	Test is repeated in 24 hr or CST is done depending on clinical situation

 

Fetal hemolytic disease

Another indication for amniocentesis is the identification and follow-up of fetal hemolytic disease in cases of isoimmunization. The procedure is usually not done until the mother's antibody titer reaches 1:8 and is rising. However, percutaneous umbilical blood sampling is now the procedure of choice to evaluate and treat fetal hemolytic disease.

 

Meconium

The presence of meconium in the amniotic fluid is usually determined by visual inspection of the sample. The significance of meconium in the fluid varies depending on when it is found.

Antepartal period. Meconium in the amniotic fluid before the beginning of labor is not usually associated with an adverse fetal outcome. The finding may be the result of acute and subsequently corrected fetal stress, chronic continuing stress, or simply the physiologic passage of meconium. Because there has been some association between meconium in amniotic fluid in the third trimester and hypertensive disorders and postmaturity, the fetus should undergo further antepartum evaluation if the birth is not imminent (Glantz & Woods, 1999).

Intrapartal period. Intrapartal meconium-stained amniotic fluid is an indication for more careful evaluation by electronic fetal monitoring and perhaps fetal scalp blood sampling. The presence of meconium, however, should not be the sole indicator for intervention.

Three possible reasons for the passage of meconium during the intrapartal period include the following: (1) it is a normal physiologic function that occurs with maturity (meconium passage being infrequent before weeks 23 or 24, with an increased incidence after 38 weeks) or with breech presentations; (2) it is the result of hypoxia-induced peristalsis and sphincter relaxation; and (3) it may be a sequela to umbilical cord compression-induced vagal stimulation in mature fetuses.

Thick, fresh meconium passed for the first time in late labor and in association with nonremediable severe variable or late fetal heart rate (FHR) decelerations is an ominous sign. The presence of meconium alone, however, is not necessarily a sign of fetal distress.

 

NURSE ALERT The birth team should be ready to suction the nasopharynx of the neonate carefully at the time of birth, ideally before the first breath is taken. Suctioning at this time effectively reduces the incidence and severity of meconium aspiration in the neonate.

 

PERCUTANEOUS UMBILICAL BLOOD

SAMPLING

Direct access to the fetal circulation during the second and third trimesters is possible through percutaneous umbilical blood sampling (PUBS), or cordocentesis, which is the most widely used method for fetal blood sampling and transfusion. PUBS involves the insertion of a needle directly into a fetal umbilical vessel under ultrasound guidance. Ideally, the umbilical cord is punctured 1 to 2 cm from its insertion into the placenta (Fig. 5). At this point the cord is well anchored and will not move, and the risk of maternal blood contamination (from the placenta) is slight. Generally, 1 to 4 ml of blood is removed and tested immediately by the Kleihauer-Betke procedure to ensure that it is fetal in origin. Indications for use of PUBS include prenatal diagnosis of inherited blood disorders, karyotyping of malformed fetuses, detection of fetal infection, determination of the acid-base status of fetuses with IUGR, and assessment and treatment of isoimmunization and thrombocytopenia in the fetus (Harmon, 1999). Complications that can occur include leaking of blood from the puncture site, cord laceration, thromboembolism, preterm labor, premature rupture of membranes, and infection.

 

Fig. 5 Technique for PUBS guided by ultrasound.

 

In fetuses at risk for isoimmune hemolytic anemia, PUBS permits precise identification of fetal blood type and RBC count and may prevent further intervention. If the fetus is positive for the presence of maternal antibodies, a direct blood test can confirm the degree of anemia resulting from hemolysis. Intrauterine transfusion of severely anemic fetuses can be done 4 to 5 weeks earlier than through the intraperitoneal route.

Follow-up includes continuous FHR monitoring for several minutes to 1 hour and a repeat ultrasound examination 1 hour later to determine that no further bleeding or hematoma formation has occurred.

 

CHORIONIC VILLUS SAMPLING

The combined advantages of earlier diagnosis and rapid results have made chorionic villus sampling (CVS) a popular technique for genetic studies, although some risks to the fetus exist. Although indications for CVS are similar to those for amniocentesis, second-trimester amniocentesis appears to be safer than CVS (Alfirevic, Gosden, & Neilson, 2001). The benefits of earlier diagnosis must be weighed against the increased risk of pregnancy loss and risk of anomalies.

The procedure is performed between 10 and 12 weeks of gestation and involves the removal of a small tissuespecimen from the fetal portion of the placenta (Fig. 6). Because chorionic villi originate in the zygote, this tissue reflects the genetic makeup of the fetus.

 

Fig. 6 Chorionic villus sampling. (Courtesy Medical and Scientific Illustration, Crozet, VA.)

 

CVS procedures can be accomplished either transcervically or transabdominally. In transcervical sampling, a sterile catheter is introduced into the cervix under continuous ultrasonographic guidance and a small portion of the chorionic villi is aspirated with a syringe. The aspiration cannula and obturator must be placed at a suitable site, and rupture of the amniotic sac must be avoided.

If the abdominal approach is used, an 18-gauge spinal needle with stylet is inserted under sterile conditions through the abdominal wall into the chorion frondosum under ultrasound guidance. The stylet is then withdrawn and the chorionic tissue is aspirated into a syringe.

Complications of the procedure include vaginal spotting or bleeding immediately afterward, miscarriage, rupture of membranes, and chorioamnionitis. Because of the possibility of fetomaternal hemorrhage, women who are Rh negative should receive immune globulin (RhoGAM) to avoid isoimmunization (Gilbert & Harmon, 1998). An increased risk of limb anomalies (transverse digital anomalies) has been noted when CVS is done before 10 weeks of gestation (Wilson, 2000).

 

MATERNAL ASSAYS

 

Alpha-fetoprotein

AFP is produced by the fetal liver, and increasing levels are detectable in the serum of pregnant women from 14 to 34 weeks. Maternal serum AFP (MSAFP) is used as a screening tool for neural tube defects (NTDs), usually between 15 and 22 weeks of gestation. MSAFP is a screening tool only and identifies candidates for the more definitive procedures of amniocentesis and ultrasound examination. Approximately 80% to 85% of all open NTDs and open abdominal wall defects can be detected early in pregnancy using these techniques. Screening is recommended for all pregnant women (ACOG, 1996). If findings are abnormal, follow-up procedures include genetic counseling for families with a history of NTD, repeat AFP, ultrasound examination, and possibly amniocentesis.

Down syndrome and probably other autosomal trisomies are associated with lower-than-normal levels of MSAFP and amniotic fluid AFP. The triple-marker test may also be performed at 16 to 18 weeks of gestation and uses the levels of MSAFP, unconjugated estriol, and human chorionic gonadotropin (hCG), in combination with maternal age, to calculate risk. In the presence of a fetus with Down syndrome, the MSAFP and unconjugated estriol levels are low, whereas the hCG level is elevated.

As with MSAFP, the triple-marker test is a screening procedure only and is not diagnostic. A definitive examination of amniotic fluid for AFP and chromosomal analysis combined with ultrasound visualization of the fetus is necessary for diagnosis; however, using these tests can reduce the number of amniocenteses needed (Egan et al., 2000).

 

Coombs' test

The indirect Coombs' test is a screening test for Rh incompatibility. If the maternal titer for Rh antibodies is greater than 1:8, amniocentesis for determination of bilirubin in amniotic fluid is indicated to establish the severity of fetal hemolytic anemia. The Coombs' test can also detect other antibodies that may place the fetus at risk for incompatibility with maternal antigens.

ELECTRONIC FETAL MONITORING

INDICATIONS

First- and second-trimester antepartal assessment is directed primarily at the diagnosis of fetal anomalies. The goal of third-trimester testing is to determine whether the intrauterine environment continues to be supportive to the fetus. The testing is often used to determine the timing of childbirth for patients at risk for uteroplacental insufficiency (UPI). This gradual loss of placental function results first in inadequate nutrient delivery to the fetus, leading to IUGR. Subsequently, respiratory function is also compromised, resulting in fetal hypoxia. Common indications for both the nonstress test (NST) and the contraction stress test (CST) are listed in Box 6.

 

Box 6 Indications for Electronic Fetal Monitoring Assessment Using NST and CST Maternal diabetes mellitus Chronic hypertension Hypertensive disorders in pregnancy IUGR Sickle cell disease Maternal cyanotic heart disease Postmaturity History of previous stillbirth Decreased fetal movement Isoimmunization Meconium-stained amniotic fluid at third-trimester amniocentesis Hyperthyroidism Collagen disease Older pregnant woman Chronic renal disease

 

No clinical contraindications exist for the NST, but results may not be conclusive if gestation is 26 weeks or less. Absolute contraindications for the CST are the following: rupture of membranes, previous classic incision for cesarean birth, preterm labor, placenta previa, and abruption placentae. Other conditions in which CST may be contraindicated are multifetal pregnancy, previous preterm labor, hydramnios, more than 36 weeks of gestation, and incompetent cervix. As a rule, reactive patterns with the NST or negative results with the CST are associated with favorable outcomes.

 

FETAL RESPONSES TO HYPOXIA OR ASPHYXIA

Hypoxia or asphyxia elicits a number of responses in the fetus. There is a redistribution of blood flow to certain vital organs. This series of responses (redistribution of blood flow favoring vital organs, decrease in total oxygen consumption, and switch to anaerobic glycolysis) is a temporary mechanism that enables the fetus to survive up to 30 minutes of limited oxygen supply without decompensation of vital organs. However, during more severe asphyxia or sustained hypoxemia, these compensatory responses are no longer maintained, and a decrease in the cardiac output, arterial blood pressure, and blood flow to the brain and heart occurs (Parer, 1999), with characteristic FHR patterns reflecting these changes.

 

Variability

Considerable evidence supports the clinical belief that FHR variability indicates an intact nervous pathway through the cerebral cortex, midbrain, vagus nerve, and cardiac conduction system. With a 98°/o accuracy in predicting fetal well-being, the presence of normal FHR variability is a reassuring indicator. Inputs from various areas of the brain decrease after cerebral asphyxia, leading to a decrease in variability after failure of the fetal hemodynamic compensatory mechanisms to maintain cerebral oxygenation (Parer, 1999).

 

NONSTRESS TEST

The nonstress test (NST) is the most widely applied technique for antepartum evaluation of the fetus. The basis for the NST is that the normal fetus will produce characteristic heart rate patterns in response to fetal movement. In the healthy fetus with an intact CNS, 90% of gross fetal body movements are associated with accelerations of the FHR. This response can be blunted by hypoxia, acidosis, drugs (analgesics, barbiturates, and beta-blockers), fetal sleep, and some congenital anomalies (Tucker, 2000).

NST can be performed easily in an outpatient setting because it is noninvasive. It is also relatively inexpensive and has no known contraindications. Disadvantages center around the high rate of false-positive results for nonreactivity as a result of fetal sleep cycles, medications, and fetal immaturity. The test is also slightly less sensitive in detecting fetal compromise than are the CST and BPP.

 

Procedure

The woman is seated in a reclining chair (or in semi-Fowler position) to avoid supine hypotension. The FHR is recorded by a Doppler transducer, and a tocotransducer is applied to detect uterine contractions or fetal movements. The strip chart is observed for signs of fetal activity and a concurrent acceleration of FHR. If evidence of fetal movement is not apparent on the strip, the woman may be asked to depress a button on a handheld event marker connected to the monitor when she feels fetal movement. The movement is then noted on the strip. Because almost all accelerations are accompanied by fetal movement, the movements need not be recorded for the test to be considered reactive. The test is usually completed within 20 to 30 minutes, but it may take longer if the fetus needs to be awakened from a sleep state.

It is common practice to ask the woman to drink orange juice or be given glucose to raise her blood sugar and thereby stimulate fetal movements. However, there is no research evidence that this practice is effective (McCarthy & Narrigan, 1995). Other methods that have been used to stimulate fetal activity, such as manipulating the woman's abdomen or using a transvaginal light, have not been very effective either. Only acoustic stimulation has had some impact (Marden et al., 1997).

Fetal acoustic stimulation. The acoustic stimulation test is another method of testing antepartum FHR response. The test takes approximately 15 minutes to complete, with the fetus monitored for 5 to 10 minutes before stimulation to obtain a baseline FHR. The sound source (usually a laryngeal stimulator) is then activated for 3 seconds on the maternal abdomen over the fetal head. Monitoring continues for another 5 minutes, after which the monitor tracing is assessed. A test is considered reactive if there is an immediate and sustained increase in long-term variability and heart rate accelerations. The accelerations produced may have a significant increase in duration. The test may be repeated at 1-minute intervals up to three times when there is no response. Further evaluation is needed with BPP or CST if the pattern is still nonreactive.

Interpretation. Generally accepted criteria for a reactive NST tracing are as follows:

• Two or more accelerations of 15 beats per minute lasting for 15 seconds over a 20-minute period

• Normal baseline rate

• Long-term variability amplitude of 10 or more beats per minute

If the test does not meet the criteria after 40 minutes, it is considered nonreactive (Fig. 7 and Table 5), in which case further assessments are needed with a CST or BPP. The current recommendation is that the NST be performed twice weekly (after 28 weeks of gestation) with patients who are diabetic or at risk for fetal death.

 

 

Fig. 7 Reactive NST (fetal heart rate acceleration with movement). (From Tucker, S. [2000]. Pocket guide to fetal monitoring and assessment [4th ed.]. St. Louis: Mosby.)

 

Table 5 Guide for Interpretation of the CST
INTERPRETATION	CLINICAL SIGNIFICANCE
NEGATIVE No late decelerations, with minimum of three uterine contractions lasting 40 to 60 sec within 10-min period (see Fig. 8, A)	Reassurance that the fetus is likely to survive labor should it occur within 1 wk; more frequent testing may be indicated by clinical situation
POSITIVE Persistent and consistent late decelerations occurring with more than half of contractions (see Fig. 8, 6)	Management lies between use of other tools of fetal assessment such as BPP and termination of pregnancy; a positive test result indicates that fetus is at increased risk for perinatal morbidity and mortality; physician may perform expeditious vaginal birth after successful induction or may proceed directly to cesarean birth; decision to intervene is determined by fetal monitoring and presence of FHR reactivity
SUSPICIOUS Late decelerations occurring in less than half of uterine contractions once adequate contraction pattern established	NST and CST should be repeated within 24 hr; if interpretable data cannot be achieved, other methods of fetal assessment must be used
HYPERSTIMULATION Late decelerations occurring with excessive uterine activity (contractions more often than every 2 min or lasting longer than 90 sec) or persistent increase in uterine tone
UNSATISFACTORY Inadequate uterine contraction pattern or tracing too poor to interpret

 

 

Fig. 8 CST. A, Negative CST. B, Positive CST. (From Tucker, S. [2000]. Pocket guide to fetal monitoring and assessment [4th ed.]. St. Louis: Mosby.)

 

CONTRACTION STRESS TEST

The contraction stress test (CST) is one of the first electronic methods to be developed for assessment of fetal health. It was devised as a graded stress test of the fetus, and its purpose was to identify the jeopardized fetus that was stable at rest but showed evidence of compromise after stress. Uterine contractions decrease uterine blood flow and placental perfusion. If this decrease is sufficient to produce hypoxia in the fetus, a deceleration in FHR will result, beginning at the peak of the contraction and persisting after its conclusion (late deceleration).

 

 

NURSE ALERT. In a healthy fetoplacental unit, uterine contractions usually do not produce late decelerations, whereas if there is underlying uteroplacental insufficiency, contractions will produce late decelerations.

 

The CST provides an earlier warning of fetal compromise than the NST and has fewer false-positive results. In addition to the contraindications described earlier, the CST is more time consuming and expensive than the NST. It is also an invasive procedure if oxytocin stimulation is required.

 

Procedure

The woman is placed in a semi-Fowler position or sits in a reclining chair. External electronic monitoring is applied, and the monitor strip is observed for 10 minutes for baseline rate, long-term variability, and the possible occurrence of spontaneous contractions. The two methods of CST are the nipple-stimulated contraction test and the oxytocin-stimulated contraction test.

Nipple-stimulated contraction test. After the procedure is explained to the woman, warm, moist washcloths are applied to both breasts for several minutes. The woman is then asked to massage one nipple for 10 minutes. Massaging the nipples causes a release of oxytocin from the posterior pituitary. An alternative approach is for her to massage the nipple for 2 minutes, rest for 2 minutes, and continue for four cycles of massage and rest. If unilateral stimulation does not achieve adequate contractions (three occurring within a 10-minute window), unilateral continuous stimulation should be tried (if the intermittent approach was used), followed by bilateral stimulation for 10 minutes. When adequate contractions or hyperstimulation occurs, stimulation should be stopped. If the stimulation and rest cycle method is used, it can be performed indefinitely until considered unsuccessful (Devoe, 1995).

Oxytocin-stimulated contraction test. If nipple stimulation is not successful, an exogenous oxytocin-stimulated CST should be performed. An intravenous (IV) infusion is begun with a scalp needle. The oxytocin is diluted in an IV solution (e.g., 10 U to 1000 ml fluid), infused into the tubing of the main IV device via a piggyback port, and delivered by an infusion pump to ensure accurate dosage. The oxytocin infusion is usually begun at 0.5 mU/min and increased by 0.5 mU/min at 15- to 30-minute intervals until three uterine contractions of good quality are observed within a 10-minute period. The typical rate of oxytocin infusion used to elicit uterine contractions is 4 to 5 mU/min, and rarely is more than 8 mU/min required. The infusion rate should probably not be increased to more than 20 mU/min; however, each case should be assessed individually (Devoe, 1995).

 

Interpretation

If no late decelerations are observed with the contractions, the findings are considered negative (Fig. 8, A). Repetitive late decelerations render the test results positive (Fig. 8, B) (see Table 5).

After interpretation of the FHR pattern, the oxytocin infusion is halted and the maintenance IV solution infused until uterine activity has returned to the prestimulation level. If the CST is negative, the IV device is removed and the fetal monitor disconnected. If the CST is positive, continued monitoring and further evaluation of fetal wellbeing are indicated.

 

NURSING ROLE IN ANTEPARTAL ASSESSMENT FOR RISK

The nurse's role is that of educator and support person when the woman is undergoing such examinations as ultrasonography, MRI, CVS, PUBS, and amniocentesis. In some instances the nurse may assist the physician with the procedure. In many antepartal settings, nurses perform NSTs, CSTs, and BPPs; conduct an initial assessment; and begin necessary interventions for nonreassuring patterns. These nursing procedures are performed after additional education and training, under guidance of established protocols, and in collaboration with physicians (Treanor, 1998). Patient teaching, which is an integral component of this role, involves preparing the patient for the procedure, interpreting the findings, and providing psychosocial support when needed (Lowe et al., 1998).

 

PSYCHOLOGIC CONSIDERATIONS

All women who undergo antepartal assessments are at risk for real and potential problems and may be in an anxious frame of mind (Santalahti et al., 1996) (see Research box). In most instances the tests are ordered because of suspected fetal compromise, deterioration of a maternal condition, or both. In the third trimester, pregnant women are most concerned about protecting themselves and their fetuses and consider themselves most vulnerable to outside influences. The label of high risk will increase this sense of vulnerability.

PSYCHOLOGIC IMPLICATIONS OF HIGH RISK PREGNANCY

When a woman is diagnosed with a high risk pregnancy, she and her family will likely experience stress related to the diagnosis. The woman may exhibit various psychologic responses, including anxiety, low self-esteem, guilt, frustration, and inability to function. The development of a high risk pregnancy can also affect parental attachment, accomplishment of the tasks of pregnancy, and family adaptation to the pregnancy (Ramer & Frank, 2001).

If the woman is fearful for her own well-being, she may continue to feel ambivalence about the pregnancy or not accept the reality of the pregnancy. She may not be able to complete preparations for the baby or go to childbirth classes if she is on bed rest or hospitalized. The family may become frustrated because they cannot engage in activities that prepare them for parenthood.

Antepartal hospitalization is an added stressor for the high risk pregnant woman and her family. The woman may be lonely because she is separated from her home and family. She may feel powerless and unable to make decisions for herself because her care is out of her control.

Likewise, preparation for the birth process may be out of control of the woman and her family. Unexpected procedures and care for the woman or fetus may take priority over the usual birth plan and may not allow for choices that would have been selected if the pregnancy had been normal.

Attachment to the newborn can be affected if the mother or newborn is ill after the birth. Early contact may not be possible. Time, support, and intervention by the health care team may be necessary to help the family begin the attachment process.

The nurse can help the woman and her family regain control and balance in their lives by providing support and encouragement, providing information about the pregnancy problem and its management (see Resources at end of chapter), and providing opportunities to make as many choices as possible about the woman's care.

The impact of the effects of a specific pregnancy complication and its management is discussed in the following chapters.

 

RESEARCH Women's Perception of Risk in Complicated Pregnancies Researchers have suggested that patients assess their own health risks based on worldviews, experiences, competing stressors, social support, and self-esteem. When patients do not agree with their health care provider regarding their health risk status, they may not comply with treatment plans. A heightened sense of risk may lead to unnecessary anxiety and unnecessary interventions. In pregnancy, health care providers calculate the biomedical risk using a number of variables from patient history and current pregnancy. To explore women's perceptions of risks in pregnancy, a survey that included 103 ambulatory women with uncomplicated pregnancies and 105 women hospitalized for pregnancy complications was conducted in western Canada. Women with complications were described as having significantly lower income and education and were more likely to be nonwhite. The perception of pregnancy risk (dependent variable) was correlated with biomedical risk, self-esteem, social support, stress, and anxiety (independent variables). There were significant positive correlations between perception of risk score and the biomedical risk score in both groups. In the complications group, anxiety correlated positively with perception of risk, and this perception increased with history of previous pregnancy complications and number of days currently in the hospital. There were no differences between the two groups in stress, selfesteem, or social support. IMPLICATIONS FOR PRACTICE A thorough prenatal nursing assessment should include asking the woman about her perception of risk for herself and her baby. If the woman is at high risk for complications, the nurse can help the patient develop a realistic view of her situation and encourage her to engage in behaviors (e.g., managing anxiety and adhering to treatments) that increase her chances of a positive pregnancy outcome.