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648

Assessment

for Risk Factors

C h a p t e r

DEITRA LEONARD LOWDERMILK

21

• Explore physiologic and psychologic aspects ofhigh risk pregnancy.

• Discuss regionalization of health care services.• Examine risk factors identified through history,

physical examination, and diagnostic tech-niques.

• Differentiate among diagnostic techniques, in-cluding when they are used in pregnancy andfor what purposes.

• Develop a teaching plan to explain diagnostictechniques and implications of findings to pa-tients and their families.

LEARNING OBJECTIVES

acoustic stimulation test Antepartum test to elicitfetal heart rate response to sound; performed byapplying sound source (laryngeal stimulator) tomaternal abdomen over the fetal head

alpha-fetoprotein (AFP) Fetal antigen; elevated lev-els in amniotic fluid and maternal blood are asso-ciated with neural tube defects

amniocentesis Procedure in which a needle is in-serted through the abdominal and uterine walls toobtain amniotic fluid; used for assessment of fe-tal health and maturity

amniotic fluid index (AFI) Estimation of amount ofamniotic fluid by means of ultrasound to determineexcess or decrease

biophysical profile (BPP) Noninvasive assessmentof the fetus and its environment using ultra-sonography and fetal monitoring; includes fetalbreathing movements, gross body movements, fe-tal tone, reactive fetal heart rate, and qualitativeamniotic fluid volume

chorionic villus sampling (CVS) Removal of fetal tis-sue from placenta for genetic diagnostic studies

contraction stress test (CST) Test to stimulate uter-ine contractions for the purpose of assessing fetal response; a healthy fetus does not react tocontractions, whereas a compromised fetus

demonstrates late decelerations in the fetal heartrate that are indicative of uteroplacental insuffi-ciency

daily fetal movement count (DFMC) Maternal as-sessment of fetal activity; the number of fetalmovements within a specified time are counted;also called “kick count”

Doppler blood flow analysis Use of ultrasound fornoninvasive measurement of blood flow in the fe-tus and placenta

magnetic resonance imaging (MRI) Noninvasivenuclear procedure for imaging tissues with high fatand water content; in obstetrics, uses include eval-uation of fetal structures, placenta, and amnioticfluid volume

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

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

uteroplacental insufficiency (UPI) Decline in pla-cental function (exchange of gases, nutrients, andwastes) leading to fetal hypoxia and acidosis; ev-idenced by late decelerations of the fetal heart ratein response to uterine contractions

KEY TERMS AND DEFINITIONS

ELECTRONIC RESOURCESAdditional information related to the content in Chapter 21 can be found on

the companion website at http://evolve.elsevier.com/Lowdermilk/Maternity/• NCLEX Review Questions• WebLinks

or on the interactive companion CD • NCLEX Review Questions

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C H A P T E R 21 Assessment for Risk Factors 649

Approximately 500,000 of the 4 millionbirths that occur in the United Stateseach year will be categorized as highrisk because of maternal or fetal com-

plications. Identification of the risks, together with appro-priate and timely intervention during the perinatal period,can prevent morbidity and mortality among mothers and in-fants.

With the changing demographics in the United States,more women and families can be identified as at risk becauseof factors other than biophysical criteria. The increasingnumbers of homeless, single, or uninsured pregnant womenwho have no access to prenatal care during any stage of preg-nancy and the behaviors and lifestyles that pose a risk to thehealth of the mother and fetus contribute to the problem(U.S. Department of Health and Human Services [USD-HHS], 2000).

Care of these high risk patients requires the unified effortsof medical and nursing personnel. The high risk patient andthe factors associated with a diagnosis of high risk are iden-tified in this chapter; diagnostic techniques used to moni-tor the maternal-fetal unit are emphasized.

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

High risk pregnancy is a critical problem for modern med-ical and nursing care. The new social emphasis on the qual-ity of life and the wanted child has resulted in a reductionof family size and the number of unwanted pregnancies. Atthe same time, technologic advances have facilitated preg-nancies in previously infertile couples. As a consequence,emphasis is on the safe birth of normal infants who can de-velop to their potential. Scientific and technologic advanceshave allowed perinatal health care to reach a level far beyondthat previously available.

The diagnosis of high risk imposes a situational crisis onthe family (e.g., loss of pregnancy before the anticipated date,development of gestational diabetes mellitus with its po-tential complications, or birth of a neonate who does notmeet cultural, societal, or familial norms and expectations).

Maternal Health ProblemsThe leading causes of maternal death attributable to preg-nancy differ over the world. In general, three major causeshave persisted for the last 50 years: hypertensive disorders,infection, and hemorrhage. The three leading causes of ma-ternal mortality today are gestational hypertension, pul-monary embolism, and hemorrhage. Factors that are stronglyrelated to maternal death include age (younger than 20 years

DEFINITION AND SCOPE OF THE PROBLEM

and 35 years or older), lack of prenatal care, low educationalattainment, unmarried status, and nonwhite race. African-American maternal mortality rates are more than three timeshigher than those for Caucasian women (Kochanek, Murphy,Anderson, & Scott, 2004). Reaching the goal set by HealthyPeople 2010 of no more than 3.3 maternal deaths per 100,000live births (USDHHS, 2000) will be a significant challenge.

Although the overall number of maternal deaths is small,maternal mortality remains a significant problem because ahigh proportion of deaths are preventable, primarilythrough improving the access to and use of prenatal careservices. Nurses can be instrumental in educating the pub-lic about the importance of obtaining early and regular careduring pregnancy.

Fetal and Neonatal HealthProblemsThe leading cause of death in the neonatal period is con-genital anomalies (Arias, MacDorman, Strobino, & Guyer,2003). Other causes of neonatal death include disorders re-lated to short gestation and low birth weight, sudden infantdeath, respiratory distress syndrome, and the effects of ma-ternal complications. Racial differences in the infant mor-tality rates continue to challenge public health experts. In-creased rates of survival during the neonatal period haveresulted largely from high quality prenatal care and the im-provement in perinatal services, including technologic ad-vances in neonatal intensive care and obstetrics.

What can be done to prevent antepartum fetal deaths?Some factors are presumed avoidable, such as failure to re-spond appropriately to abnormalities of pregnancy and la-bor. Such abnormalities may include results of fetal growthor fetal well-being assessments, significant maternal weightloss, or decreased fetal movements (Druzin, Gabbe, & Reed,2002). In addition, commitment at national, state, and lo-cal levels is required to reduce the infant mortality rate. Moreresearch is needed to identify the extent to which financial,educational, sociocultural, and behavioral factors individu-ally and collectively affect perinatal morbidity and mortal-ity. Barriers to care must be removed and perinatal servicesmodified to meet contemporary health care needs.

Regionalization of Health Care ServicesEarly and ongoing risk assessment is a crucial component ofperinatal care. Conditions associated with perinatal mor-bidity and mortality can be prevented, treated, or referredto more skilled health care providers. Factors to considerwhen determining a patient’s risk status include resourcesavailable locally to treat the condition, availability of ap-propriate facilities for transport if needed, and determinationof the best match for the patient’s needs.

Not all facilities develop and maintain the full spectrumof services required for high risk perinatal patients. As a con-sequence, regionalization of hospital-based perinatal healthcare services—facilities within a geographic region organizedto provide different levels of care—emerged. This system of


650 U N I T S E V E N COMPLICATIONS OF CHILDBEARING

coordinated care was also applied to preconception and am-bulatory prenatal care services.

Guidelines have been established regarding the level ofcare that could be expected at any given facility. In ambu-latory settings, providers must distinguish themselves by thelevel of care they provide. Basic care is provided by obstetri-cians, family physicians, certified nurse-midwives, and otheradvanced practice clinicians approved by local governance.Routine risk-oriented prenatal care, education, and supportis provided. Providers offering specialty care are obstetricianswho must provide fetal diagnostic testing and managementof obstetric and medical complications in addition to basiccare. Subspecialty care is provided by maternal-fetal medicinespecialists and includes the aforementioned in addition togenetic testing, advanced fetal therapies, and managementof severe maternal and fetal complications (American Acad-emy of Pediatrics [AAP] & American College of Obstetriciansand Gynecologists [ACOG], 2002).

In hospital settings, perinatal services also are designatedas basic, specialty, or subspecialty. Criteria for basic perinatalservices include care of all patients admitted to the service,with an established triage system for high risk patients whoshould be transferred to a higher level of care; ability to per-form a cesarean birth within 30 minutes of a decision to doso; availability of blood and blood products; availability ofradiology, anesthesia, and laboratory services on a 24-hourbasis; presence of nursery and postpartum care; resuscitationand stabilization of all neonates born in the hospital; avail-ability of transport for all sick neonates; family visitation; anddata collection and retrieval (AAP & ACOG, 2002).

Specialty hospital care includes these requirements in ad-dition to care of high risk mothers and fetuses, stabilizationof ill neonates before transfer, and care of preterm infantswith a birth weight of 1500 g or more. Women in pretermlabor or those with impending births at 32 weeks of gesta-tion or less should be transferred for subspecialty care. Ad-ditional criteria for subspecialty care include provision ofcomprehensive perinatal care for women and infants of allrisk categories, evaluation and use of new high risk tech-nologies and therapies, and data collection and retrieval. Col-laboration among providers to meet the patient’s needs isthe key in reducing perinatal morbidity and mortality (AAP& ACOG, 2002).

Assessment of Risk FactorsPregnancies can be designated as high risk for any of severalundesirable outcomes. Those considered to be at risk foruteroplacental insufficiency (UPI; the gradual decline in de-livery of needed substances by the placenta to the fetus) carrya serious threat for fetal growth restriction, intrauterine fe-tal death, intrapartum death, intrapartum fetal distress, andvarious types of neonatal morbidity.

In the past, risk factors were evaluated only from a med-ical viewpoint; therefore only adverse medical, obstetric, or physiologic conditions were considered to place the woman at risk. Today, a more comprehensive approach tohigh risk pregnancy is used, and the factors associated with

high risk childbearing are grouped into broad categoriesbased on threats to health and pregnancy outcome (seeGuidelines/Guías box). Categories of risk are biophysical,

GUIDELINES/GUÍAS

High Risk Factors

HIGH RISK POTENTIAL ASSESSMENT PROBLEM

• Have you had any problems General assessmentwith this pregnancy?

• ¿Ha tenido problemascon este embarazo?

• Have you had blurred Preeclampsiavision?

• ¿Ha tenido visiónborrosa?

• Have you had severe Preeclampsiaheadaches?

• ¿Ha tenido doloresfuertes de cabeza?

• Have you had Cardiac diseasedifficulty breathing?

• ¿Ha tenido dificultadpara respirar?

• Have you had heart Cardiac diseasepalpitations?

• ¿Ha tenido palpitacionesdel corazón?

• Have you been vomiting? Hyperemesis • ¿Ha tenido vómitos? gravidarum

• Have you had any Sexually transmittedinfections? infections or

• ¿Ha tenido alguna vaginal infectionsinfección?

• Have you had swelling? Preeclampsia• ¿Ha tenido hinchazón?

• Were all your pregnancies Preterm laborterm?

• ¿Llegaron a las cuarentasemanas todos susembarazos?

• Have you ever had Diabetesdiabetes?

• ¿Ha tenido diabetes?

• Have you ever had Gestational high blood pressure? hypertension

• ¿Ha tenido alta presión Chronic hypertensionsanguínea?

• Have you ever had anemia? Anemia• ¿Ha estado anémica?

• Do you take drugs? Substance abusePrescription medicine?

• ¿Usa drogas? ¿Medicinarecetada?

• Do you drink alcohol? Substance abuseSmoke?

• ¿Toma bebidasalcohólicas? ¿Fuma?



Categories of High Risk Factors

BIOPHYSICAL FACTORS

• Genetic considerations. Genetic factors may interfere withnormal fetal or neonatal development, result in congen-ital anomalies, or create difficulties for the mother. Thesefactors include defective genes, transmissible inheriteddisorders and chromosomal anomalies, multiple preg-nancy, large fetal size, and ABO incompatibility.

• Nutritional status. Adequate nutrition, without which fe-tal growth and development cannot proceed normally, isone of the most important determinants of pregnancyoutcome. Conditions that influence nutritional status in-clude the following: young age; three pregnancies in theprevious 2 years; tobacco, alcohol, or drug use; inade-quate dietary intake because of chronic illness or foodfads; inadequate or excessive weight gain; and hematocritvalue less than 33%.

• Medical and obstetric disorders. Complications of currentand past pregnancies, obstetric-related illnesses, andpregnancy losses put the patient at risk (see Box 21-2).

PSYCHOSOCIAL FACTORS

• Smoking. A strong, consistent, causal relation has beenestablished between maternal smoking and reduced birthweight. Risks include low-birth-weight infants, higherneonatal mortality rates, increased miscarriages, and in-creased incidence of premature rupture of membranes.These risks are aggravated by low socioeconomic status,poor nutritional status, and concurrent use of alcohol.

• Caffeine. Birth defects in humans have not been relatedto caffeine consumption. High intake (three or more cupsof coffee per day) has been related to a slight decreasein birth weight.

• Alcohol. Although its exact effects in pregnancy have notbeen quantified and its mode of action is largely unex-plained, alcohol exerts adverse effects on the fetus, re-sulting in fetal alcohol syndrome, fetal alcohol effects,learning disabilities, and hyperactivity.

• Drugs. The developing fetus may be adversely affectedby drugs through several mechanisms.They can be ter-atogenic, cause metabolic disturbances, produce chem-ical effects, or cause depression or alteration of centralnervous system function. This category includes med-ications prescribed by a health care provider or boughtover the counter, as well as commonly abused drugssuch as heroin, cocaine, and marijuana. (See Chap-ter 22 for more information about drug and alcoholabuse.)

• Psychologic status. Childbearing triggers profound andcomplex physiologic, psychologic, and social changes,with evidence to suggest a relation between emotionaldistress and birth complications. This risk factor includesconditions such as specific intrapsychic disturbances andaddictive lifestyles; a history of child or spouse abuse; in-adequate support systems; family disruption or dissolu-tion; maternal role changes or conflicts; noncompliancewith cultural norms; unsafe cultural, ethnic, or religiouspractices; and situational crises.

SOCIODEMOGRAPHIC FACTORS

• Low income. Poverty underlies many other risk factorsand leads to inadequate financial resources for food andprenatal care, poor general health, increased risk of med-ical complications of pregnancy, and greater prevalenceof adverse environmental influences.

• Lack of prenatal care. Failure to diagnose and treat com-plications early is a major risk factor arising from finan-cial barriers or lack of access to care; depersonalizationof the system resulting in long waits, routine visits, vari-ability in health care personnel, and unpleasant physicalsurroundings; lack of understanding of the need for earlyand continued care or cultural beliefs that do not supportthe need; and fear of the health care system and itsproviders.

• Age. Women at both ends of the childbearing age spec-trum have a higher incidence of poor outcomes; however,age may not be a risk factor in all cases. Both physiologicand psychologic risks should be evaluated.a. Adolescents. More complications are seen in young

mothers (younger than 15 years), who have a 60%higher mortality rate than those older than 20 years,and in pregnancies occurring less than 6 years aftermenarche. Complications include anemia, preeclamp-sia, prolonged labor, and contracted pelvis andcephalopelvic disproportion. Long-term social impli-cations of early motherhood are lower educational sta-tus, lower income, increased dependence on govern-ment support programs, higher divorce rates, andhigher parity.

b. Mature mothers. The risks to older mothers are notfrom age alone but from other considerations such asnumber and spacing of previous pregnancies; geneticdisposition of the parents; and medical history,lifestyle, nutrition, and prenatal care. The increasedlikelihood of chronic diseases and complications thatarises from more invasive medical management of apregnancy and labor combined with demographiccharacteristics put an older woman at risk. Medicalconditions more likely to be experienced by maturewomen include hypertension and preeclampsia, dia-betes, extended labor, cesarean birth, placenta previa,abruptio placentae, and mortality. Her fetus is atgreater risk for low birth weight and macrosomia,chromosomal abnormalities, congenital malforma-tions, and neonatal mortality.

• Parity.The number of previous pregnancies is a risk fac-tor associated with age and includes all first pregnancies,especially a first pregnancy at either end of the child-bearing age continuum. The incidence of preeclampsiaand dystocia is higher with a first birth.

• Marital status.The increased mortality and morbidity ratesfor unmarried women, including a greater risk forpreeclampsia, are often related to inadequate prenatalcare and a younger childbearing age.

• Residence. The availability and quality of prenatal carevaries widely with geographic residence. Women inmetropolitan areas have more prenatal visits than dothose in rural areas, who have fewer opportunities for

BOX 21-1

Continued


psychosocial, sociodemographic, and environmental (Gilbert& Harmon, 2003) (Box 21-1).

Biophysical risks include factors that originate within themother or fetus and affect the development or functioningof either one or both. Examples include genetic disorders,nutritional and general health status, and medical or obstetric-related illnesses.

Psychosocial risks consist of maternal behaviors and ad-verse lifestyles that have a negative effect on the health ofthe mother or fetus. These risks may include emotional dis-tress and disturbed interpersonal relationships, as well as in-adequate social support and unsafe cultural practices.

Sociodemographic risks arise from the mother and herfamily. These risks may place the mother and fetus at risk.Examples include lack of prenatal care, low income, mari-tal status, and ethnicity (see Box 21-1). Environmental fac-tors include hazards in the workplace and the woman’s gen-eral environment and may include environmental chemicals(e.g., pesticides, lead, and mercury), radiation, and pollutants(Silbergeld & Patrick, 2005).

Risk factors are interrelated and cumulative in their ef-fects. Box 21-2 lists specific pregnancy problems and risk fac-tors. Risk factors for the postpartum woman and newbornare shown in Box 21-3.

The development of a comprehensive database for preg-nancy risk assessment will help generate appropriate nurs-ing diagnoses. For example, use of functional health patternscan be the basis for an assessment tool (Box 21-4).

The major expected outcome of all antepartum testing is thedetection of potential fetal compromise. Ideally the tech-nique used identifies fetal compromise before intrauterineasphyxia of the fetus so that the health care provider can takemeasures to prevent or minimize adverse perinatal outcomes.No single test can provide this information. Assessment tests

ANTEPARTUM TESTING: BIOPHYSICAL ASSESSMENT

should be selected based on their effectiveness, and the re-sults must be interpreted in light of the complete clinical pic-ture. The most reliable evidence for effectiveness is providedby randomized controlled trials. Nurses can be informedabout the most recent research on fetal assessment by usingan up-to-date systematic review such as the Cochrane Data-base of Systematic Reviews (Enkin et al., 2001). Table 21-1lists the evidence for recommending care for fetal assessmentscreening based on this database.

Daily Fetal Movement CountAssessment of fetal activity by the mother is a simple yetvaluable method for monitoring the condition of the fetus.The daily fetal movement count (DFMC) (also called “kickcounts”) can be done at home, is noninvasive, is simple tounderstand, and usually does not interfere with a daily rou-tine. The DMFC is frequently used to monitor the fetus inpregnancies complicated by conditions that may affect fe-tal oxygenation. These conditions include but are not lim-ited to gestational hypertension or chronic hypertension anddiabetes. The presence of movements is generally a reassuringsign of fetal health.

Several protocols are used for counting. One recommen-dation is to count once a day for 60 minutes and another com-mon recommendation is that mothers count fetal activity twoor three times daily for 60 minutes each time. Except for es-tablishing a very low number of daily fetal movements or atrend toward decreased motion, the clinical value of the ab-solute number of fetal movements has not been established,except in the situation in which fetal movements cease entirelyfor 12 hours (the so-called fetal alarm signal). A count of fewerthan three fetal movements within 1 hour warrants further eval-uation by a nonstress test (NST) or contraction stress test(CST), biophysical profile (BPP), or a combination of these (seelater discussion). Women should be taught the significance ofthe presence and/or absence of fetal movements, the proce-dure for counting that is to be used, how to record findingson a DFM record, and when to notify the health care provider.


Categories of High Risk Factors—cont’d

SOCIODEMOGRAPHIC FACTORS–cont’d

specialized care and consequently a higher incidenceof maternal mortality. Health care in the inner city,where residents are usually poorer and beginchildbearing earlier and continue for longer, may be oflower quality than in a more affluent neighborhood.

• Ethnicity. Although ethnicity by itself is not a major risk,race is an indicator of other sociodemographic risk fac-tors. Nonwhite women are more than 3 times as likely asCaucasian women to die of pregnancy-related causes.African-American babies have the highest rates of pre-maturity and low birth weight, with the infant mortalityrate among African-Americans being more than doublethat among Caucasians.

ENVIRONMENTAL FACTORS

• Various environmental substances can affect fertility andfetal development, the chance of a live birth, and thechild’s subsequent mental and physical development. En-vironmental influences include infections, radiation,chemicals such as pesticides, therapeutic drugs, illicitdrugs, industrial pollutants, cigarette smoke, stress, anddiet. Paternal exposure to mutagenic agents in the work-place has been associated with an increased risk of mis-carriage.

BOX 21-1



Specific Pregnancy Problems and Related Risk Factors

PRETERM LABOR

Age younger than 16 or older than 35 yearsLow socioeconomic statusMaternal weight below 50 kgPoor nutritionPrevious preterm birthIncompetent cervixUterine anomaliesSmokingDrug addiction and alcohol abusePyelonephritis, pneumoniaMultiple gestationAnemiaAbnormal fetal presentationPreterm rupture of membranesPlacental abnormalitiesInfectionAbdominal surgery in current pregnancyHistory of cervical surgery

POLYHYDRAMNIOS

Diabetes mellitusMultiple gestationFetal congenital anomaliesIsoimmunization (Rh or ABO)Nonimmune hydropsAbnormal fetal presentation

INTRAUTERINE GROWTH RESTRICTION (IUGR)

Multiple gestationPoor nutrition

Maternal cyanotic heart diseasePrior pregnancy with IUGRMaternal collagen diseasesChronic hypertensionPreeclampsiaRecurrent antepartum hemorrhageSmokingMaternal diabetes with vascular problemsFetal infectionsFetal cardiovascular anomaliesDrug addiction and alcohol abuseFetal congenital anomaliesHemoglobinopathies

OLIGOHYDRAMNIOS

Renal agenesis (Potter’s syndrome)Prolonged rupture of membranesIUGRIntrauterine fetal death

POSTTERM PREGNANCY

AnencephalyPlacental sulfatase deficiencyPerinatal hypoxia, acidosisPlacental insufficiency

CHROMOSOMAL ABNORMALITIES

Maternal age 35 years or olderBalanced translocation (maternal and paternal)

BOX 21-2

Reference: Gillem-Goldstein, J. et al. (2003). Methods of assessment for pregnancy at risk. In A. DeCherney, A., & L. Nathan (Eds.), Current obstetric andgynecologic diagnosis and treatment (9th ed.). New York: Lange Medical Books/McGraw-Hill.

Factors That Place the Postpartum Woman and Neonate at High Risk

MOTHER

HemorrhageInfectionAbnormal vital signsTraumatic labor or birthPsychosocial factors

INFANT (FOR ADMISSION TO NICU)High Risk

Infants who continue with or develop signs of RDS orother respiratory distress

Asphyxiated infants (Apgar score less than 6 at 5 min),resuscitation required at birth

Preterm infants, dysmature infantsInfants with cyanosis or suspected cardiovascular dis-

ease, persistent cyanosisInfants with major congenital malformations requiring

surgery, chromosomal anomaliesInfants with convulsions, sepsis, hemorrhagic diathesis,

or shockMeconium aspiration syndrome

CNS depression for more than 24 hrHypoglycemiaHypocalcemiaHyperbilirubinemia

Moderate Risk

DysmaturityPrematurity (weight between 2000 and 2500 g)Apgar score less than 5 at 1 minFeeding problemsMultifetal birthTransient tachypneaHypomagnesemia or hypermagnesemiaHypoparathyroidismFailure to gain weightJitteriness or hyperactivityCardiac anomalies not requiring immediate catheteriza-

tionHeart murmurAnemiaCNS depression for less than 24 hr

BOX 21-3

CNS, Central nervous system; NICU, neonatal intensive care unit; RDS, respiratory distress syndrome.

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Assessment for High Risk Pregnancy with Functional Health Patterns

For each of the following functional health patterns, thenurse includes questions that will provide data about thewoman, her family, her community, and her cultural prac-tices and beliefs:

• Health perception or health management pattern. Cur-rent health, medical history, family medical history, en-vironmental or chemical exposure, family decisionmaking about health, community resources, beliefsabout health care during pregnancy

• Nutritional-metabolic pattern. Nutritional status, knowl-edge of pregnancy needs, pregnancy discomforts,community resources (WIC), cultural eating practices

• Elimination pattern. Urinary and bowel patterns, fam-ily or cultural practices (laxatives), community wasteand sanitation services

• Activity-exercise pattern. Usual exercise, recreation,community resources, cultural practices or taboos foractivities during pregnancy

• Sleep-rest pattern. Usual sleep patterns, use of reme-dies, family sleep arrangements, cultural beliefsabout sleep and rest in pregnancy

• Cognitive-perceptual pattern. Communication prob-lems, knowledge deficits about pregnancy and birth(individual and family), community resources for sup-port for high risk pregnant patients, cultural beliefsabout pain and its management

• Self-perception or self-concept pattern. Body image,responses of family to high risk pregnancy, housingconditions, cultural practices about parenting

• Role-relationship pattern. Feelings of security, occu-pation, hobbies, family living arrangements, com-munity resources

• Sexuality-reproductive pattern. Sexual activities,problems, restrictions, obstetric history, current ob-stetric status, cultural beliefs about sexual practicesduring pregnancy

• Coping-stress pattern. Life stressors, losses experi-enced, coping mechanisms, support systems, com-munity resources, spiritual or religious practices or be-liefs that are important

BOX 21-4

References: Gilbert, E., & Harmon, J. (2003). Manual of high risk pregnancy and delivery (3rd ed.). St. Louis: Mosby; Gordon, M. (2002). Manual of nursingdiagnosis (10th ed.). St. Louis: Mosby.WIC, special Supplemental Nutrition Program for Women, Infants, and Children.

TABLE 21-1

Fetal Assessment Screening: Recommendations for Care

RECOMMENDATION FETAL ASSESSMENT TEST OR 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 Effects likely to be beneficialtrimesters

• Ultrasound use to confirm suspected multiple pregnancy• Ultrasound use for placental location in suspected placenta previa• Ultrasound use to assess amniotic fluid volume• Early second trimester amniocentesis for identification of chromosomal

abnormalities• Transabdominal instead of transvaginal chorionic villus sampling (CVS)

• Formal systems of risk scoring Trade-off between beneficial • Routine use of early ultrasound and adverse effects• CVS versus amniocentesis for diagnosing chromosomal abnormalities• Serum alpha-fetoprotein screening for neural tube defects• Triple screen test for Down syndrome and neural tube defects

• Placental grading by ultrasound to improve perinatal outcome Unknown effectiveness• Biophysical profile for fetal surveillance• Routine fetal movement counts to improve perinatal outcome

• Routine use of ultrasound for fetal anthropometry (body measurements) Unlikely to be beneficialin late pregnancy

• Use of Doppler ultrasound screening in all pregnancies• Measurement of placental hormones (estriol and human placental

lactogen)

• Nipple stimulation test to improve perinatal outcome Likely to be ineffective or harmful• Nonselective nonstress test to improve perinatal outcome• Contraction stress test to improve perinatal outcome

Source: Enkin, M. et al. (2001). Effective care in pregnancy and childbirth: A synopsis. Birth, 28(1), 41-51.

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In assessing fetal movements, it is im-portant to remember that they are usually not presentduring the fetal sleep cycle; they may be temporarily re-duced if the woman is taking depressant medications,drinking alcohol, or smoking a cigarette. They do not de-crease as the woman nears term. Obesity decreases theability of the mother to perceive fetal movement.

UltrasonographySound is a form of wave energy that causes small particlesin a medium to oscillate. The frequency of sound, whichrefers to the number of peaks or waves that move over agiven point per unit of time, is expressed in hertz (Hz).Sound with a frequency of 1 cycle, or one peak per second,has a frequency of 1 Hz. When directional beams of soundstrike an object, an echo is returned. The time delay betweenthe emission of the sound and the return of the echo andthe direction of the echo are noted. From these data, the dis-tance and location of an object can be calculated. Ultrasoundis sound frequency higher than that detectable by humans(greater than 20,000 Hz). Diagnostic ultrasound instrumentsoperate within a frequency range of 2 to 10 million Hz (or2 to 10 MHz), which is below the range used by sonar andradar equipment. Ultrasound images are a reflection of thestrength of the sending beam, the strength of the returningecho, and the density of the medium (e.g., muscle [uterus],bone, tissue [placenta], fluid, or blood through which thebeam is sent and returned) (Chervenak & Gabbe, 2002).

Diagnostic ultrasonography is an important, safe tech-nique in antepartum fetal surveillance. It provides critical in-formation to health care providers regarding fetal activity andgestational age, normal versus abnormal fetal growth curves,visual assistance with which invasive tests may be performedmore safely, fetal and placental anatomy, and fetal well-being (Chervenak & Gabbe, 2002). Ultrasound examinationcan be done abdominally or transvaginally during pregnancy.Both produce a three-dimensional view from which a pic-torial image is obtained. Abdominal ultrasonography is moreuseful after the first trimester when the pregnant uterus be-comes an abdominal organ. For the procedure, the womanusually should have a full bladder to displace the uterus up-ward to get a better image of the fetus. Transmission gel orpaste is applied to the woman’s abdomen before a transduceris moved over the skin to enhance transmission and recep-tion of the sound waves. She is positioned with small pillowsunder her head and knees. The display panel is positionedso that the woman and/or her partner can observe the im-ages on the screen if they desire.

Transvaginal ultrasonography, in which the probe is in-serted into the vagina, allows pelvic anatomy to be evaluatedin greater detail and intrauterine pregnancy to be diagnosedearlier (Manning, 2004). A transvaginal ultrasound exami-nation is well tolerated by most patients because it alleviatesthe need for a full bladder. It is especially useful in obesewomen whose thick abdominal layers cannot be penetratedadequately with an abdominal approach. A transvaginal ul-

NURSE ALERT trasound may be performed with the woman in a lithotomyposition or with her pelvis elevated by towels, cushions, ora folded pillow. This pelvic tilt is optimal to image the pelvicstructures. A protective cover such as a condom, the fingerof a clean rubber surgical glove, or a special probe cover pro-vided by the manufacturer is used to cover the transducerprobe. The probe is lubricated with a water-soluble gel andplaced in the vagina either by the examiner or by the womanherself. During the examination, the position of the probeor the tilt of the examining table may be changed so that thecomplete pelvis is in view. The procedure is not physicallypainful, although the woman will feel pressure as the probeis moved. Transvaginal ultrasonography is optimally used inthe first trimester to detect ectopic pregnancies, monitor thedeveloping embryo, help identify abnormalities, and helpestablish gestational age. In some instances it may be usedas an adjunct to abdominal scanning to evaluate preterm la-bor in second- and third-trimester pregnancies.

Levels of ultrasonographyPerinatal care providers and ultrasonographers have come

to a tentative agreement on terminology describing two different levels of ultrasonography. The basic screening or limited examination is used most frequently and can be performed by ultrasonographers or other health care pro-fessionals, including nurses, who have had special training.Indications for limited ultrasonography are described in de-tail in the next section; its primary use is to detect fetal vi-ability, determine the presentation of the fetus, assess ges-tational age, locate the placenta, examine the fetal anatomyfor malformations, and determine amniotic fluid volume(AFV). Targeted or comprehensive examinations are per-formed if a woman is suspected of carrying an anatomicallyor a physiologically abnormal fetus. Indications for a com-prehensive examination include abnormal findings on clin-ical examination, especially with polyhydramnios or oligo-hydramnios, elevated alpha-fetoprotein (AFP) levels, and ahistory of offspring with anomalies that can be detected byultrasound examination. Comprehensive ultrasonography isperformed by highly trained and experienced personnel.

Indications for useMajor indications for obstetric sonography appear by

trimester in Table 21-2. During the first trimester, ultrasoundexamination is performed to obtain information regarding(1) number, size, and location of gestational sacs; (2) pres-ence or absence of fetal cardiac and body movements; (3) presence or absence of uterine abnormalities (e.g., bi-cornuate uterus or fibroids) or adnexal masses (e.g., ovariancysts or an ectopic pregnancy); (4) date of pregnancy (bymeasuring the crown-rump length); and (5) presence and lo-cation of an intrauterine contraceptive device.

During the second and third trimesters, information re-garding the following conditions is sought: (1) fetal viabil-ity, number, position, gestational age, growth pattern, andanomalies; (2) AFV; (3) placental location and maturity;



(4) uterine fibroids and anomalies; (5) adnexal masses; and(6) cervical length.

Ultrasonography provides earlier diagnoses, allowing ther-apy to be instituted early in the pregnancy, thereby de-creasing the severity and duration of morbidity, both phys-ical and emotional, for the family. For instance, earlydiagnosis of a fetal anomaly gives the family choices such as(1) intrauterine surgery or other therapy for the fetus, (2) ter-mination of the pregnancy, or (3) preparation for the careof an infant with a disorder.

Fetal heart activity. Fetal heart activity can bedemonstrated as early as 6 to 7 weeks by real-time echo scan-ners and at 10 to 12 weeks by Doppler mode. By 9 to 10 weeks,gestational trophoblastic disease can be diagnosed. Fetaldeath can be confirmed by lack of heart motion, the pres-ence of fetal scalp edema, and maceration and overlap of thecranial bones.

Gestational age. Gestational dating by ultra-sonography is indicated for conditions such as (1) uncertaindates for the last normal menstrual period, (2) recent dis-continuation of oral contraceptives, (3) bleeding episode dur-ing the first trimester, (4) uterine size that does not agree withdates, and (5) other high risk conditions.

During the first 20 weeks of gestation, ultrasonographyprovides an accurate assessment of gestational age becausemost normal fetuses grow at the same rate. Accuracy is in-creased as the fetus ages because more than one variable ismeasured. The four methods of fetal age estimation used in-clude (1) determination of gestational sac dimensions (atabout 8 weeks), (2) measurement of crown-rump length (be-tween 7 and 12 weeks), (3) measurement of the biparietal di-ameter (BPD) (after 12 weeks), and (4) measurement of fe-mur length (after 12 weeks). Fetal BPD at 36 weeks shouldbe approximately 8.7 cm. Term pregnancy and fetal matu-rity can be diagnosed with some confidence if the biparietalmeasurement by ultrasound examination is greater than 9.8 cm (Fig. 21-1), especially when this is combined with ap-propriate femur length measurement.

In later gestational periods, serial measurements can pro-vide a more accurate determination of fetal age. Two andpreferably three composite measurements are recom-mended, at least 2 weeks apart, and these are plotted againststandard fetal growth curves. This method, when applied be-tween 24 and 32 weeks of gestation, yields an estimation er-ror of 10 days more or less than the actual age (Manning,2004).

Fetal growth. Fetal growth is determined by both in-trinsic growth potential and environmental factors. Condi-tions that require ultrasound assessment of fetal growth in-clude (1) poor maternal weight gain or pattern of weightgain, (2) previous intrauterine growth restriction (IUGR), (3) chronic infections, (4) ingestion of drugs (tobacco, al-cohol, over-the-counter, and street drugs), (5) maternal di-abetes mellitus, (6) hypertension, (7) multifetal pregnancy,and (8) other medical or surgical complications.

Serial evaluations of BPD, limb length, and abdominalcircumference (AC) (Fig. 21-2) can allow differentiationamong size discrepancy resulting from inaccurate dates, trueIUGR, and macrosomia. IUGR may be symmetric (the fe-


TABLE 21-2

Major Uses of Ultrasonography during Pregnancy

FIRST TRIMESTER SECOND TRIMESTER THIRD TRIMESTER

Confirm gestational ageConfirm viabilityDetect macrosomiaDetect congenital anomaliesDetect IUGRDetermine fetal positionDetect placenta previa or abruptio

placentaeUse for visualization during amnio-

centesis, external versionBiophysical profileAmniotic fluid volume assessmentDoppler flow studiesDetect placental maturity

Establish or confirm datesConfirm viabilityDetect polyhydramnios, oligohy-

dramniosDetect congenital anomaliesDetect intrauterine growth restric-

tion (IUGR)Confirm placenta placementUse for visualization during amnio-

centesis

Confirm pregnancyConfirm viabilityDetermine gestational ageRule out ectopic pregnancyDetect multiple gestationUse for visualization during chori-

onic villus samplingDetect maternal abnormalities such

as bicornuate uterus, ovariancysts, fibroids

Fig. 21-1 Real-time image of fetal biparietal diameters at18 weeks. (From Athey, P., & Hadlock, F. [1985]. Ultrasound inobstetrics and gynecology [2nd ed.]. St. Louis: Mosby.)


tus is small in all parameters) or asymmetric (head and bodygrowth vary). Symmetric IUGR reflects a chronic or long-standing insult and may be caused by low genetic growth potential, intrauterine infection, undernutrition, heavy smok-ing, or chromosomal aberration. Asymmetric growth suggestsan acute or late-occurring deprivation, such as placental in-sufficiency resulting from hypertension, renal disease, or car-diovascular disease. Reduced fetal growth is still one of themost frequent conditions associated with stillbirth.

Macrosomic infants (those weighing 4000 g or more) are atincreased risk for traumatic injury, and asphyxia during birth.In addition, fetal macrosomia associated with maternal glu-cose intolerance or diabetes carries an increased risk of in-trauterine fetal death. Macrosomia in the infant of a diabeticmother is asymmetric and characterized by increases in fatand muscle in the abdomen and shoulders, while head cir-cumference remains normal. Macrosomia in an infant whose

mother is obese without glucose intolerance results in sym-metric changes—excessive growth of abdominal and head cir-cumferences (Chervenak & Gabbe, 2002).

Fetal anatomy. Anatomic structures that can beidentified by ultrasonography (depending on the gestationalage) include the following: head (including ventricles andblood vessels) (Fig. 21-3), neck, spine, heart, stomach, smallbowel, liver, kidneys, bladder, and limbs. Ultrasonographypermits the confirmation of normal anatomy, as well as thedetection of major fetal malformations. The presence of ananomaly may influence the location of birth (e.g., a deliveryroom versus a labor-delivery-recovery room or a subspecialtycenter versus a basic care center) and the method of birth(vaginal versus cesarean) to optimize neonatal outcomes.

The number of fetuses and their presentations also maybe assessed by ultrasonography, allowing plans for therapyand method of birth to be made in advance.

Fetal genetic disorders and physical anom-alies. A prenatal screening technique called fetal nuchal


HC

AC

Fig. 21-2 A, Appropriate planes of sections (dotted lines)for head circumference (HC), and abdominal circumference(AC). B, Real-time ultrasound image demonstrates typical headand body images that correspond to planes in A. By use ofthese two images, biparietal diameter (BPD) (7.9 cm), head cir-cumference (30 cm), abdominal circumference (28 cm), andestimated fetal weight (1840 g) in this normal 32-week fetuscan be determined. (From Athey, P., & Hadlock, F. [1985]. Ul-trasound in obstetrics and gynecology [2nd ed.]. St. Louis:Mosby.)

A

B

Fig. 21-3 Two views of the fetus during ultrasonography.A, Fetal face (20 weeks). B, Umbilical cord (26 weeks). (Cour-tesy Advanced Technology Laboratories, Bothell, WA.)

A

B


translucency (FNT) screening uses ultrasound measurementof fluid in the nape of the fetal neck between 10 and 14weeks of gestation to identify possible fetal abnormalities.A finding of abnormal fluid collection that is greater than2.5 mm is considered abnormal, whereas a measurement of3 mm or greater is highly indicative of genetic disordersand/or physical anomalies. If the FNT is abnormal, diag-nostic genetic testing is recommended (ACOG, 2004).

Placental position and function. The patternof uterine and placental growth and the fullness of the ma-ternal bladder influence the apparent location of the pla-centa by ultrasonography. During the first trimester, differ-entiation between the endometrium and small placenta isdifficult. By 14 to 16 weeks, the placenta is clearly defined;but if it is seen to be low lying, its relation to the internalcervical os can sometimes be dramatically altered by vary-ing the fullness of the maternal bladder. In approximately15% to 20% of all pregnancies in which ultrasound scanningis performed during the second trimester, the placenta seemsto be overlying the os, but the incidence of placenta previaat term is only 0.5%. Therefore the diagnosis of placenta pre-via can seldom be confirmed before 27 weeks, primarily be-cause of the elongation of the lower uterine segment as preg-nancy advances.

Another use for ultrasonography is grading of placentalmaturation. Calcium deposits are of significance in posttermpregnancies because as they increase, the available surfacearea that can be adequately bathed by maternal blood de-creases. The point at which this results in fetal wastage andhypoxia cannot be determined precisely; however, the effectsare usually observable by 42 weeks and are progressive(Gilbert & Harmon, 2003).

Adjunct to other invasive tests. The safety ofamniocentesis is increased when the positions of the fetus,placenta, and pockets of amniotic fluid can be identified ac-curately. Ultrasound scanning has reduced risks previouslyassociated with amniocentesis, such as fetomaternal hem-orrhage from a pierced placenta. Percutaneous umbilicalblood sampling (PUBS) and chorionic villus sampling alsoare guided by ultrasonography to identify the cord andchorion frondosum accurately (see Fig. 21-3, B).

Fetal well-beingPhysiologic parameters of the fetus that can be assessed

with ultrasound scanning include AFV, vascular waveformsfrom the fetal circulation, heart motion, fetal breathingmovements (FBMs), fetal urine production, and fetal limband head movements. Assessment of these parameters, singlyor in combination, yields a fairly reliable picture of fetal well-being. The significance of these findings is discussed in thefollowing sections.

Doppler blood flow analysis. One of the ma-jor advances in perinatal medicine is the ability to studyblood flow noninvasively in the fetus and placenta with ul-trasound. Doppler blood flow analysis is a helpful adjunctin the management of pregnancies at risk because of hy-

pertension, IUGR, diabetes mellitus, multiple fetuses, orpreterm labor.

When a sound wave is reflected from a moving target,there is a change in frequency of the reflected wave relativeto the transmitted wave. This is called the Doppler effect. Anultrasound beam scattered by a group of red blood cells(RBCs) is an example of this effect. The velocity of the RBCscan be determined by measuring the change in the frequencyof the sound wave reflected off the cells (Fig. 21-4).

The shifted frequencies can be displayed as a plot of ve-locity versus time, and the shape of these waveforms can beanalyzed to give information about blood flow and resist-ance in a given circulation. Velocity waveforms from um-bilical and uterine arteries, reported as systolic/diastolic(S/D) ratios, can be first detected at 15 weeks of pregnancy.Because of the progressive decline in resistance in both theumbilical and uterine arteries, this ratio decreases as preg-nancy advances. Most fetuses will achieve an S/D ratio of3 or less by 30 weeks. Persistent elevation of S/D ratios af-ter 30 weeks is associated with IUGR, usually resulting fromUPI (Druzin, Gabbe, & Reed, 2002). In postterm pregnan-cies evaluated by Doppler umbilical flow studies, an elevatedS/D ratio indicates a poorly perfused placenta. Abnormal re-sults also are seen with certain chromosome abnormalities(trisomy 13 and 18) in the fetus and with lupus erythe-matosus in the mother. Exposure to nicotine from maternalsmoking also has been reported to increase the S/D ratio.

Amniotic fluid volume. Abnormalities in AFV arefrequently associated with fetal disorders. Subjective deter-minants of oligohydramnios (decreased fluid) include the ab-sence of fluid pockets in the uterine cavity and the impres-sion of crowding of small fetal parts. An objective criterionof decreased AFV is met if the largest pocket of fluid meas-ured in two perpendicular planes is less than 2 cm (Manning,2004). In polyhydramnios (increased fluid), subjective cri-teria include multiple large pockets of fluid, the impressionof a floating fetus, and free movement of fetal limbs. Thediagnosis may be made when the largest pocket of fluid ex-ceeds 8 cm in two perpendicular planes (Chervenak &Gabbe, 2002).

The total AFV can be evaluated by a method in which thedepths (in centimeters) of the amniotic fluid in all four quad-


Fig. 21-4 Umbilical artery velocity waveform in a 17-weekfetus with S/D ratio of 4.4, which is normal for this stage.(Courtesy Michael S. Clement, MD, Mesa, AZ.)


rants surrounding the maternal umbilicus are totaled, pro-viding an amniotic fluid index (AFI). An AFI less than 5 cmindicates oligohydramnios; 5 to 19 cm is considered a nor-mal measurement; and a measurement greater than 20 cmreflects polyhydramnios (Chervenak & Gabbe, 2002).Oligohydramnios is associated with congenital anomalies(such as renal agenesis), growth restriction, and fetal distressduring labor. Polyhydramnios is associated with neural tubedefects (NTDs), obstruction of the fetal gastrointestinal tract,multiple fetuses, and fetal hydrops.

Biophysical profile. Real-time ultrasound permitsdetailed assessment of the physical and physiologic charac-teristics of the developing fetus and cataloging of normal andabnormal biophysical responses to stimuli. The biophysicalprofile (BPP) is a noninvasive dynamic assessment of a fe-tus that is based on acute and chronic markers of fetal dis-ease. The BPP includes FBMs, fetal movements, fetal tone,fetal heart rate (FHR) patterns by means of an NST, andAFV. The BPP may therefore be considered a physical ex-amination of the fetus, including determination of vitalsigns. The fetal response to central hypoxia is alteration inmovement, muscle tone, breathing, and heart rate patterns.The presence of normal fetal biophysical activities indicatesthat the central nervous system (CNS) is functional, and the

fetus therefore is not hypoxemic (Harman, 2004). BPP vari-ables and scoring are detailed in Table 21-3.

The BPP is an accurate indicator of impending fetal death.Fetal acidosis can be diagnosed early with a nonreactive NSTand absent FBMs. An abnormal BPP score and oligohy-dramnios are indications that labor should be induced (Har-man, 2004). Fetal infection in women whose membranesrupture prematurely (at less than 37 weeks of gestation) canbe diagnosed early by changes in biophysical activity thatprecede the clinical signs of infection and indicate the ne-cessity for immediate birth. When the BPP score is normaland the risk of fetal death low, intervention is indicated onlyfor obstetric or maternal factors.

Nursing roleAlthough a growing number of nurses perform ultrasound

scans and BPPs in certain centers, the main role of nurses isin counseling and educating women about the procedure(Garcia et al., 2002). Providing accurate information regardingthe procedure is imperative to allay the mother’s anxiety. Al-though ultrasound scanning has become a widely used di-agnostic tool, recommendations for the procedure are basedon expectations of a fetal problem and therefore may causeconcern. Women should be provided ample opportunity to


TABLE 21-3

Biophysical Profile

VARIABLES NORMAL (SCORE � 2) ABNORMAL (SCORE � 0)

SCORE

Reference: Harman, C. (2004). Assessment of fetal health. In R. Creasy, R. Resnik, & J. Iams (Eds.), Maternal-fetal medicine: Principles and practice (5th ed.).Philadelphia: Saunders.

6�4

EquivocalAbnormal

8-10 (if amniotic fluid index is ade-quate)

Normal

Pockets absent or pocket �1 cm intwo perpendicular planes

One or more pockets of fluid meas-uring �1 cm in two perpendicularplanes

Qualitative amniotic fluid volume

Less than two episodes of accelera-tion or acceleration of �15beats/min in 20 min

Two or more episodes of accelera-tion (�15 beats/min) in 20 min,each lasting �15 sec and associ-ated with fetal movement

Reactive fetal heart rate

Slow extension with return to flex-ion, movement of limb in full ex-tension, or fetal movement absent

One or more episodes of active ex-tension with return to flexion offetal limb(s) or trunk; opening andclosing of hand is considered nor-mal tone

Fetal tone

Less than three episodes of body orlimb movements in 30 min

Three or more discrete body or limbmovements in 30 min (episodesof active continuous movementare considered as a single move-ment)

Gross body movements

Episodes absent or no episode �30 sec in 30 min

One or more episodes in 30 min,each lasting �30 sec

Fetal breathing movements


ask questions and be reassured that the procedure is safe. Inthe 30 years that diagnostic ultrasonography has been used,no conclusive evidence of any harmful effects on humanshas emerged. Although the possibility of unidentified bio-logic effects exists, the benefits to the patient of prudent useof diagnostic ultrasonography appear to outweigh any pos-sible risk (Chervenak & Gabbe, 2002).

Performance of Limited UltrasoundExaminations

Nurses who have the training and competence may per-form limited ultrasound examinations if it is within thescope of practice in their state or area and consistentwith regulations of the agencies in which they practice(Menihan, 2000). Limited ultrasound examinations in-clude identification of fetal number, fetal presentation,fetal cardiac activity, location of the placenta, and BPP,including AFV assessment. Women should be informedabout the limited information provided by these ex-aminations. They are not meant to evaluate or identifyfetal anomalies, assess fetal age, or estimate fetalweight (Stringer, Miesnik, Brown, Menei, & Macones,2003). The obstetric health care provider is responsiblefor obtaining a more comprehensive ultrasound ex-amination when complete patient assessment is nec-essary (Association of Women’s Health, Obstetric andNeonatal Nurses [AWHONN], 1998).

Magnetic Resonance ImagingMagnetic resonance imaging (MRI) is a noninvasive radi-ologic technique used for obstetric and gynecologic diag-nosis. Like computed tomography (CT), MRI provides ex-cellent pictures of soft tissue. Unlike CT, ionizing radiationis not used; therefore vascular structures within the body canbe visualized and evaluated without injection of an iodinatedcontrast medium, thus eliminating any known biologic risk.Like sonography, MRI is noninvasive and can provide im-ages in multiple planes, but there is no interference fromskeletal, fatty, or gas-filled structures, and imaging of deeppelvic structures does not require a full bladder.

With MRI, the examiner can evaluate (1) fetal structure(CNS, thorax, abdomen, genitourinary tract, muscu-loskeletal system) and overall growth; (2) placenta (position,density, and presence of gestational trophoblastic disease);(3) quantity of amniotic fluid; (4) maternal structures (uterus,cervix, adnexa, and pelvis); (5) biochemical status (pH,adenosine triphosphate content) of tissues and organs; and(6) soft-tissue, metabolic, or functional anomalies.

The woman is placed on a table in the supine positionand slid into the bore of the main magnet, which is similarin appearance to a CT scanner. Depending on the reason forthe study, the procedure may take from 20 to 60 minutes,during which time the woman must be perfectly still exceptfor short respites. Because of the long time needed to pro-duce MRIs, the fetus will probably move, which will obscureanatomic details. The only way to ensure that this does notoccur is to administer a sedative to the mother, but this ap-

LEGAL TIP

proach should be reserved for selected cases in which visu-alization of fetal detail is critical.

MRI has little effect on the fetus; concerns that the FHRor fetal movement would decrease have not been sup-ported.

Biochemical assessment involves biologic examination (e.g.,as chromosomes in exfoliated cells) and chemical determi-nations (e.g., lecithin/sphingomyelin [L/S] ratio and biliru-bin level) (Table 21-4). Procedures used to obtain the neededspecimens include amniocentesis, PUBS, chorionic villussampling, and maternal sampling (Box 21-5).

AmniocentesisAmniocentesis is performed to obtain amniotic fluid, whichcontains fetal cells. Under direct ultrasonographic visuali-zation, a needle is inserted transabdominally into the uterus,amniotic fluid is withdrawn into a syringe, and the variousassessments are performed (Fig. 21-5). Amniocentesis is pos-sible after week 14 of pregnancy, when the uterus becomesan abdominal organ, and sufficient amniotic fluid is avail-able for testing. Indications for the procedure include pre-natal diagnosis of genetic disorders or congenital anomalies(NTDs in particular), assessment of pulmonary maturity, anddiagnosis of fetal hemolytic disease.

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

• Maternal: Hemorrhage, fetomaternal hemorrhage withpossible maternal Rh isoimmunization, infection, la-bor, abruptio placentae, inadvertent damage to the in-testines or bladder, and amniotic fluid embolism. Be-cause of the possibility of fetomaternal hemorrhage,it is standard practice after an amniocentesis to ad-minister RhoD immune globulin to the woman whois Rh negative.

• Fetal: Death, hemorrhage, infection (amnionitis), di-rect injury from the needle, miscarriage or preterm la-bor, and leakage of amniotic fluid

Many of the complications have been minimized oreliminated by using ultrasonography to direct the procedure.

BIOCHEMICAL ASSESSMENT


Fetal Rights

Amniocentesis, percutaneous umbilical blood sampling(PUBS), and chorionic villus sampling (CVS) are prena-tal tests used for diagnosing fetal defects in pregnancy.They are invasive and carry risks to the mother and fe-tus. A consideration of induced abortion is linked to theperformance of these tests because there is no treatmentfor genetically affected fetuses; therefore the issue of fe-tal rights is a key ethical concern in prenatal testing forfetal defects.

BOX 21-5


Indications for useGenetic concerns. Prenatal assessment of genetic

disorders is indicated in women older than 35 years (Box 21-6), with a previous child with a chromosomal abnor-mality, or with a family history of chromosomal anomalies.Inherited errors of metabolism (such as Tay-Sachs disease,

hemophilia, and thalassemia) and other disorders for whichmarker genes are known also may be detected. Fetal cells arecultured for karyotyping of chromosomes (see Chapter 7).Karyotyping also permits determination of fetal sex, whichis important if an X-linked disorder (occurring almost alwaysin a male fetus) is suspected.


TABLE 21-4

Summary of Biochemical Monitoring Techniques

TEST POSSIBLE FINDINGS CLINICAL SIGNIFICANCE

MATERNAL BLOOD

Coombs’ test Titer of 1:8 and increasing Significant Rh incompatibilityAFP See below

AMNIOTIC FLUID ANALYSIS

Color Meconium Possible hypoxia or asphyxiaLung profile Fetal lung maturityL/S ratio �2:1

Phosphatidylglycerol PresentCreatinine �2 mg/dl Gestational age �36 weeks

Bilirubin (�OD, 450/nm) �0.015 Gestational age �36 weeks, normal pregnancyHigh levels Fetal hemolytic disease in Rh isoimmunized pregnancies

Lipid cells �10% Gestational age �35 weeksAFP High levels after 15-week gestation Open neural tube or other defectOsmolality Decline after 20-week gestation Advancing gestational ageGenetic disorders Dependent on cultured cells for Counseling possibly required

Sex-linked karyotype and enzymatic activityChromosomalMetabolic

AFP, Alpha-fetoprotein; L/S, lecithin-sphingomyelin.

CELLULAR COMPONENTSCELLULAR COMPONENTS

Uterine wall

Placenta

Amniotic cavity

(Cell culture)

CENTRIFUGE

AMNIOCENTESIS

(direct examination)Sex chromatinBiochemical studiesEnzyme studies

SUPERNATANTRh antibodiesChemical analysisIntrauterine infection

Chromosome analysisBiochemical analysis

Enzyme studies

Fig. 21-5 A, Amniocentesis and laboratory use of amniotic fluid aspirant. B,Transabdominalamniocentesis. (B, Courtesy Marjorie Pyle, RNC, Lifecircle, Costa Mesa, CA.)

A B


Biochemical analysis of enzymes in amniotic fluid can de-tect inborn errors of metabolism. For example, AFP levelsin amniotic fluid are assessed as a follow-up for elevated lev-els in maternal serum. High AFP levels in amniotic fluid helpconfirm the diagnosis of an NTD such as spina bifida oranencephaly or an abdominal wall defect such as om-phalocele. The elevation results from the increased leakageof cerebrospinal fluid into the amniotic fluid through theclosure defect. AFP levels may also be elevated in a normalmultifetal pregnancy and with intestinal atresia, presumablycaused by lack of fetal swallowing.

A concurrent test that finds the presence of acetyl-cholinesterase almost always indicates a fetal defect (Jenkins& Wapner, 2004). In such instances, follow-up ultrasound ex-amination is recommended.

Fetal maturity. Accurate assessment of fetal matu-rity is possible through examination of amniotic fluid or itsexfoliated cellular contents. The laboratory tests describedare determinants of term pregnancy and fetal maturity (seeTable 21-4). A quick means of determining an approximateL/S ratio is the shake test foam test, or bubble stability test.Serial dilutions of fresh amniotic fluid are mixed withethanol and shaken. After 15 minutes, the amount of bub-bles present at different dilutions indicates the presence ofsurfactant.

Fetal hemolytic disease. Another indication foramniocentesis is the identification and follow-up of fetal he-molytic disease in cases of isoimmunization. The procedureis usually not done until the mother’s antibody titer reaches1:8 and is increasing. Currently PUBS is the procedure ofchoice to evaluate and treat fetal hemolytic disease.

Meconium. The presence of meconium in the am-niotic fluid is usually determined by visual inspection of thesample. The significance of meconium in the fluid varies de-pending on when it is found.

Antepartal period. Meconium in the amniotic fluidbefore the beginning of labor is not usually associated withan adverse fetal outcome. The finding may be the result ofacute and subsequently corrected fetal stress, chronic con-tinuing stress, or simply the physiologic passage of meco-nium. Because there has been some association betweenmeconium in amniotic fluid in the third trimester and hy-

pertensive disorders and postmaturity, the fetus should un-dergo further antepartum evaluation if the birth is not im-minent (Glantz & Woods, 2004).

Intrapartal period. Intrapartal meconium-stainedamniotic fluid is an indication for more careful evaluationby electronic fetal monitoring (EFM) and perhaps fetal scalpblood sampling. The presence of meconium, however,should not be the sole indicator for intervention.

Three possible reasons for the passage of meconium dur-ing the intrapartal period are as follows: (1) it is a normalphysiologic function that occurs with maturity (meconiumpassage being infrequent before weeks 23 or 24, with an increased incidence after 38 weeks); (2) it is the result of hypoxia-induced peristalsis and sphincter relaxation; and (3)it may be a sequel to umbilical cord compression–inducedvagal stimulation in mature fetuses. Thick, fresh meconiumpassed for the first time in late labor and in association withnonremediable severe variable or late FHR decelerations isan ominous sign.

The birth team should be ready to suctionthe nasopharynx of the neonate carefully at the time ofbirth, ideally before the first breath is taken. Suctioningat this time may reduce the incidence and severity ofmeconium aspiration in the neonate, however the prac-tice is being challenged. At least one study has foundno difference in suctioned versus unsuctioned infants.

Chorionic Villus SamplingThe combined advantages of earlier diagnosis and rapid re-sults have made chorionic villus sampling (CVS) a popu-lar technique for genetic studies, although some risks to thefetus exist. Although indications for CVS are similar to thosefor amniocentesis, second-trimester amniocentesis appearsto be safer than CVS (Alfirevic, Sundberg, & Brigham, 2003).The benefits of earlier diagnosis must be weighed against theincreased risk of pregnancy loss and risk of anomalies.

The procedure is performed between 10 and 12 weeks ofgestation and involves the removal of a small tissue speci-men from the fetal portion of the placenta (Fig. 21-6). Be-cause chorionic villi originate in the zygote, this tissue re-flects the genetic makeup of the fetus.

CVS procedures can be accomplished either transcervi-cally or transabdominally. In transcervical sampling, a ster-ile catheter is introduced into the cervix under continuousultrasonographic guidance, and a small portion of the chori-onic villi is aspirated with a syringe. The aspiration cannulaand obturator must be placed at a suitable site, and ruptureof the amniotic sac must be avoided.

If the abdominal approach is used, an 18-gauge spinalneedle with stylet is inserted under sterile conditions throughthe abdominal wall into the chorion frondosum under ul-trasound guidance. The stylet is then withdrawn, and thechorionic tissue is aspirated into a syringe (see Fig. 21-6).

Complications of the procedure include vaginal spottingor bleeding immediately afterward, miscarriage (in 0.3% of

NURSE ALERT


Elimination of Maternal Age as anIndication for Invasive Prenatal Diagnosis

Maternal age of 35 years and older has been a standardindication for invasive prenatal testing since 1979 despitea sensitivity of only 30%. The importance of age as a sin-gle indication for testing is being reevaluated, as serumscreening has evolved. The most effective use of re-sources involves screening the whole population of preg-nant women. Presently many centers offer the option of screening before invasive testing for women over 35 years of age (Jenkins & Wapner, 2004).

BOX 21-6


cases), rupture of membranes (in 0.1% of cases), andchorioamnionitis (in 0.5% of cases). Because of the possi-bility of fetomaternal hemorrhage, women who are Rh neg-ative should receive immune globulin to avoid isoimmu-nization (Gilbert & Harmon, 2003). An increased risk of limbanomalies (transverse digital anomalies) has been noted whenCVS is done before 10 weeks of gestation (Wilson, 2000).

Use of amniocentesis and CVS is declining because ofadvances in noninvasive screening techniques. These tech-niques include measurement of nuchal translucency, ma-ternal serum screening tests in the first and secondtrimesters, and ultrasonography in the second trimester(Benn, Egan, Fang, & Smith-Bindman, 2004).

Percutaneous Umbilical BloodSamplingDirect access to the fetal circulation during the second andthird trimesters is possible through percutaneous umbilicalblood sampling (PUBS), or cordocentesis, which is the mostwidely used method for fetal blood sampling and transfu-sion. PUBS involves the insertion of a needle directly intoa fetal umbilical vessel under ultrasound guidance. Ideally,the umbilical cord is punctured 1 to 2 cm from its insertioninto the placenta (Fig. 21-7) (Simpson, 2002). At this pointthe cord is well anchored and will not move, and the risk ofmaternal blood contamination (from the placenta) is slight.Generally, 1 to 4 ml of blood is removed and tested imme-diately by the Kleihauer-Betke procedure to ensure that itis fetal in origin. Indications for use of PUBS include pre-natal diagnosis of inherited blood disorders, karyotyping ofmalformed fetuses, detection of fetal infection, determina-tion of the acid-base status of fetuses with IUGR, and assessment and treatment of isoimmunization and throm-

bocytopenia in the fetus (Jenkins & Wapner, 2004). Com-plications that can occur include leaking of blood from thepuncture site, cord laceration, thromboembolism, pretermlabor, premature rupture of membranes, and infection(Simpson, 2002).

In fetuses at risk for isoimmune hemolytic anemia, PUBSpermits precise identification of fetal blood type and RBCcount and may prevent the need for further intervention. Ifthe fetus is positive for the presence of maternal antibodies,a direct blood test can confirm the degree of anemia resultingfrom hemolysis. Intrauterine transfusion of severely anemicfetuses can be done 4 to 5 weeks earlier than through the in-traperitoneal route.

Follow-up includes continuous FHR monitoring for sev-eral minutes to 1 hour and a repeated ultrasound examina-tion 1 hour later to ensure that no further bleeding orhematoma formation has occurred.

Maternal AssaysAlpha-fetoproteinMaternal serum alpha-fetoprotein (AFP) (MSAFP) lev-

els have been used as a screening tool for NTDs in preg-nancy. Through this technique, approximately 80% to 85%of all open NTDs and open abdominal wall defects can bedetected early in pregnancy. Screening is recommended forall pregnant women.

The cause of NTDs is not well understood, but 95% ofall affected infants are born to women with no family his-tory of similar anomalies (Jenkins & Wapner, 2004). The de-fect occurs in 1 to 2 per 1000 births in most parts of theUnited States. The birth of one affected child increases therisk of NTD recurrence in future pregnancies to 1% to 5%(Fanaroff, Martin, & Rodriguez, 2004).


Aspiration withtranscervical catheter

Ultrasound

Aspiration with spinal needle

Maternal tissue

Fetal tissue(chorionic villi)

Fig. 21-6 Chorionic villus sampling. (Courtesy Medical and Scientific Illustration, Crozet, VA.)



BACKGROUND

• Women requesting prenatal genetic diagnostic testingmay have anxiety while waiting, receive false-positive re-sults (abnormal results but a normal fetus), and have alack of options if the test is abnormal. Many women wantthe testing done early enough that they may considerpregnancy termination if the results are abnormal.

• Amniocentesis is conventionally done around 16 weeksof gestation. Genetic results are returned after 18 weeks,in time for the woman to choose a second-trimester ter-mination. The wait is agonizing for parents, and second-trimester abortion is not always a personal option, nor isit always available.

• There is pressure for earlier diagnostic procedures, suchas chorionic villus sampling (CVS) of the placenta, ac-cessed either transabdominally or transcervically. Mostclinicians delay this procedure until after 9 weeks gesta-tion because of some limb reduction (missing or hy-poplastic limbs) seen after early CVS. Early amniocente-sis is another option, requiring skillful removal of amnioticfluid from the inner amniotic sac only, filtering for fetalcells, and replacing the fluid. Both early procedures maycause pregnancy loss.

OBJECTIVE

• The reviewers’ goal was to compare early and late am-niocentesis and chorionic villus sampling (both transab-dominal and transcervical) for safety and accuracy. Out-comes were the technical difficulties encountered insampling, problems with the genetic analysis, pregnancycomplications such as bleeding, leaking fluid, preterm la-bor, any pregnancy losses and still births, and neonatalabnormalities, such as talipes (clubfoot), hemangiomas,limb reduction, respiratory distress syndrome, low birthweight, and admission to special care nursery.

METHODS

Search Strategy

• The reviewers searched Cochrane, MEDLINE, 30 journals,and a weekly awareness search that covered 37 journals.Search keywords included amniocentesis and chorionicvillus sampling.

• There were 14 randomized studies that were acceptedinto this review, ranging in publication dates from 1986to 1999. The number of women was not reported for everystudy but totaled more than 15,000. The countries of origin included Denmark, Sweden, Finland, Italy, theUnited States, and Canada.

Statistical Analyses

• Statistical analyses allowed a weighted estimate of riskfor each outcome, and the results were pooled from thestudies.

FINDINGS

• The incidence of pregnancy loss after second-trimesteramniocentesis was 3%, which was not significantly in-creased over the general population risk of 2%. However,

FINDINGS cont’d

amniocentesis was associated with an increased risk ofspontaneous miscarriage and amniotic fluid leakage. Second-trimester amniocentesis was safer and easierthan early amniocentesis, with fewer fetal anomalies,fewer needle inserts, fewer lab failures (because ofinadequate fetal cells), and fewer false negatives.Trans-cervical CVS was associated with significantly morepregnancy loss, more lab failures, and more vaginalbleeding than second-trimester amniocentesis. Trans-abdominal CVS appears to be safer than the transcervicalprocedure. Early amniocentesis appeared to cause morespontaneous miscarriage than transabdominal CVS.Theincidence of anomalies was not increased significantly.

LIMITATIONS

• The expertise of the operators varied, as CVS was fairlynew in 1991. This, however, may not necessarily be a lim-itation, because it reflects the reality that there are alwayspractitioners of varying skill levels practicing. Some stud-ies “randomized” by giving women the choice of proce-dures. During the course of some of the trials, informa-tion became publicized about CVS leading to limbreduction (never replicated in later, larger studies), andso recruitment and dropouts became a problem. None ofthe trials assessed the laboratory accuracy adequately.One large trial excluded 70% of potential CVS-random-ized women because of placental position, thus reducinggeneralizability.

CONCLUSIONS

• Second-trimester amniocentesis appears to be thesafest and most accurate prenatal diagnostic procedure.Amniocentesis should never be done before 15 weeks ofgestation. Transabdominal CVS is preferable if an earlyprocedure is warranted. If the transabdominal procedureis contraindicated, then transcervical CVS is preferred inthe first trimester and amniocentesis is preferred in thesecond trimester.

IMPLICATIONS FOR PRACTICE

• Women presented with the possibility of fetal anomaliesneed to know the risks and benefits of the diagnostic pro-cedures offered. They also need to consider the thera-peutic options available, should the results be abnormal,including the availability and acceptability of second-trimester abortion.

IMPLICATIONS FOR FURTHER RESEARCH

• Much more research needs to focus on the acceptabilityand satisfaction of women with the procedures, and theirdecision making. The unavailability of second-trimesterabortion in some areas creates hardships that deserve re-search. All new prenatal procedures should be rigorouslytested before general use. Outcomes should include an-tenatal and neonatal loss, details about anomalies, anddiagnostic accuracy. Neonatal assessors should beblinded as to procedure used.

EVIDENCE-BASED PRACTICE

Prenatal Diagnostics: Amniocentesis and Chorionic Villus Sampling

Reference: Alfirevic, Z., Sundberg, K., & Brigham, S. (2003). Amniocentesis and chorionic villi sampling for prenatal diagnosis (Cochrane Review). In The Cochrane Library, Issue 4, 2005.Chichester, UK: John Wiley & Sons.


AFP is produced by the fetal liver, and increasing levelsare detectable in the serum of pregnant women from 14 to34 weeks. Although amniotic fluid AFP is diagnostic forNTD, MSAFP is a screening tool only and identifies can-didates for the more definitive procedures of amniocente-sis and ultrasound examination. MSAFP screening can bedone with reasonable reliability any time between 15 and 22weeks of gestation (16 to 18 weeks being ideal) (Jenkins &Wapner, 2004).

Once the maternal level of AFP is determined, it is com-pared with normal values for each week of gestation. Valuesalso should be correlated with maternal age, weight, race, andwhether the woman has insulin-dependent diabetes. If find-ings are abnormal, follow-up procedures include geneticcounseling for families with a history of NTD, repeated AFP,ultrasound examination, and possibly, amniocentesis.

Down syndrome and probably other autosomal trisomiesare associated with lower-than-normal levels of MSAFP andamniotic fluid AFP. The triple-marker test also is performedat 16 to 18 weeks of gestation and uses the levels of three ma-ternal serum markers, MSAFP, unconjugated estriol, and hu-man chorionic gonadotropin (hCG), in combination withmaternal age, to calculate a new risk level. In the presence

of a fetus with Down syndrome, the MSAFP and unconju-gated estriol levels are low, whereas the hCG level is elevated.With these two additional screening tests, approximately60% of cases of Down syndrome can be identified. Othermaternal markers are being investigated as predictors of fe-tal abnormalities as well. Serum pregnancy-associated pla-cental protein A (PAPP-A) is low in Down syndrome,whereas another substance, inhibin-A, is elevated in Downsyndrome and other trisomies (Simpson, 2002).

As with MSAFP, these tests are screening procedures onlyand are not diagnostic. A definitive examination of amnioticfluid for AFP and chromosomal analysis combined with ul-trasound visualization of the fetus is necessary for diagnosis.

Coombs’ TestThe indirect Coombs’ test is a screening for Rh incom-

patibility. If the maternal titer for Rh antibodies is greaterthan 1:8, amniocentesis for determination of bilirubin in am-niotic fluid is indicated to establish the severity of fetal he-molytic anemia. Coombs’ test also can detect other anti-bodies that may place the fetus at risk for incompatibilitywith maternal antigens.

Indications

First- and second-trimester antepartal assessment is directedprimarily at the diagnosis of fetal anomalies. The goal ofthird-trimester testing is to determine whether the in-trauterine environment continues to be supportive to the

ANTEPARTAL ASSESSMENT USING ELECTRONIC FETAL MONITORING


Fig. 21-7 Technique for percutaneous umbilical bloodsampling guided by ultrasound.

Critical Thinking ExerciseDown Syndrome

Patty and David, both 37 years old, are expecting theirfirst baby. Patty is 8 weeks pregnant and is worried aboutthe risk of their baby being born with Down syndrome.She tells the nurse that she is relieved to be having an ul-trasound done today because the procedure will showwhether or not the baby has Down syndrome and shewon’t have to have other tests. What response by thenurse to Patty’s statement would be appropriate?1 Evidence—Is there sufficient evidence to draw con-

clusions about what response the nurse should give?2 Assumptions—Describe underlying assumptions

about the following issues:a. Maternal age and risk of Down syndromeb. Ultrasound use by trimesterc. Screening versus diagnosis for Down syndrome

3 What implications and priorities for nursing care canbe made at this time?

4 Does the evidence objectively support your conclu-sion?

5 Are there alternative perspectives to your conclusion?

��


fetus. The testing is often used to determine the timing ofchildbirth for women at risk for UPI. Gradual loss of pla-cental function results first in inadequate nutrient deliveryto the fetus, leading to IUGR. Subsequently, respiratoryfunction also is compromised, resulting in fetal hypoxia.Common indications for both the NST and the CST arelisted in Box 21-7.

No clinical contraindications exist for the NST, but re-sults 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 cesareanbirth, preterm labor, placenta previa, and abruptio placen-tae. Other conditions in which the CST may be con-traindicated are multifetal pregnancy, previous preterm la-bor, hydramnios, more than 36 weeks of gestation, andincompetent cervix. As a rule, reactive patterns with the NSTor negative results with the CST are associated with favor-able outcomes.

Fetal Responses to Hypoxia and AsphyxiaObservable fetal responses to hypoxia or asphyxia are theclinical basis for testing with EFM. Hypoxia or asphyxia elic-its a number of responses in the fetus. Blood flow is redis-tributed to certain vital organs. This series of responses (re-distribution of blood flow favoring vital organs, decrease intotal oxygen consumption, and switch to anaerobic glycol-ysis) is a temporary mechanism that enables the fetus to sur-vive up to 30 minutes of limited oxygen supply without de-compensation of vital organs. However, during more severeasphyxia or sustained hypoxemia, these compensatory re-sponses are no longer maintained, and a decrease in the car-diac output, arterial blood pressure, and blood flow to the

brain and heart occurs with characteristic FHR patterns re-flecting these changes (Parer & Nageotte, 2004).

VariabilityConsiderable evidence supports the clinical belief that

FHR variability indicates an intact nervous pathwaythrough the cerebral cortex, midbrain, vagus nerve, and car-diac conduction system. With 98% accuracy in predictingfetal well-being, the presence of normal FHR variability isa reassuring indicator. Inputs from various areas of the braindecrease after cerebral asphyxia, leading to a decrease in vari-ability after failure of the fetal hemodynamic compensatorymechanisms to maintain cerebral oxygenation (Parer & Nageotte, 2004).

Nonstress TestThe nonstress test (NST) is the most widely applied tech-nique for antepartum evaluation of the fetus. It is an idealscreening test and is the primary method of antepartum fe-tal assessment at most sites. The basis for the NST is that thenormal fetus will produce characteristic HR patterns in re-sponse to fetal movement. In the healthy fetus with an in-tact CNS, 90% of gross fetal body movements are associatedwith accelerations of the FHR. The acceleration with move-ment response may be blunted by hypoxia, acidosis, drugs(analgesics, barbiturates, and beta-blockers), fetal sleep, andsome congenital anomalies (Tucker, 2004). The NST can beperformed easily and quickly in an outpatient setting becauseit is noninvasive, is relatively inexpensive, and has no knowncontraindications. Disadvantages center around the high rateof false-positive results for nonreactivity as a result of fetalsleep cycles, chronic tobacco smoking, medications, and fe-tal immaturity. The test also is slightly less sensitive in de-tecting fetal compromise than are the CST or BPP.

ProcedureThe woman is seated in a reclining chair (or in semi-

Fowler position) with a slight left tilt to optimize uterine per-fusion and avoid supine hypotension. The FHR is recordedwith a Doppler transducer, and a tocodynamometer is ap-plied to detect uterine contractions or fetal movements. Thetracing is observed for signs of fetal activity and a concur-rent acceleration of FHR. If evidence of fetal movement isnot apparent on the tracing, the woman may be asked to de-press a button on a hand-held event marker connected to themonitor when she feels fetal movement. The movement isthen noted on the tracing. Because almost all accelerationsare accompanied by fetal movement, the movements neednot be recorded for the test to be considered reactive. Thetest is usually completed within 20 to 30 minutes, but it maytake longer if the fetus must be awakened from a sleep state.

It has been suggested that the woman drink orange juiceor be given glucose to increase her blood sugar level andthereby stimulate fetal movements. This practice is common;however, research has not proven this practice to be effec-


Indications for Electronic Fetal MonitoringAssessment Using NST and CST

• Maternal diabetes mellitus• Chronic hypertension• Hypertensive disorders in pregnancy• Intrauterine growth restriction• 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

NST, nonstress test; CST, contraction stress test.

BOX 21-7


tive (Tan & Sabapathy, 2001). Some sources suggest that fe-tal movements increase when maternal glucose levels are low.Other methods that have been used to stimulate fetal ac-tivity, such as manipulating the woman’s abdomen or usinga transvaginal light, have not been very effective either. Onlyvibroacoustic stimulation has had some impact (Tan &Smyth, 2001).

InterpretationGenerally accepted criteria for a reactive tracing are as fol-

lows:

• Two or more accelerations of 15 beats/min lasting for15 seconds over a 20-minute period

• Normal baseline rate

• Long-term variability amplitude of 10 or morebeats/min

If the test does not meet the criteria after 40 minutes, itis considered nonreactive (Fig. 21-8 and Table 21-5), in whichcase further assessments are needed with a CST or BPP. Thecurrent recommendation is that the NST be performed twice

weekly (after 28 weeks of gestation) with women who havediabetes or are at risk for having a fetal death (Druzin,Gabbe, & Reed, 2002).

Vibroacoustic StimulationVibroacoustic stimulation (also called fetal acoustic stimu-lation test) is another method of testing antepartum FHRresponse and is sometimes used in conjunction with theNST. The test takes approximately 15 minutes to complete,with the fetus monitored for 5 to 10 minutes before stimu-lation to obtain a baseline FHR. If the fetal baseline patternis nonreactive, the sound source (usually a laryngeal stimu-lator) is then activated for 3 seconds on the maternal ab-domen over the fetal head. Monitoring continues for an-other 5 minutes, after which the monitor tracing is assessed.A test is considered reactive if there is an immediate and sus-tained increase in long-term variability and HR accelerations.The accelerations produced may have a significant increasein duration. The test may be repeated at 1-minute intervalsup to 3 times when there is no response. Further evaluation


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TABLE 21-5

Interpretation of the Nonstress Test

RESULT INTERPRETATION CLINICAL SIGNIFICANCE

Reactive Two or more accelerations of FHR of 15 beats/min As long as twice-weekly NSTs remain reactive, lasting � 15 sec, associated with each fetal most high risk pregnancies are allowed to movement in 20-min period continue

Nonreactive Any tracing with either no FHR accelerations or Further indirect monitoring may be attemptedaccelerations �15 beats/min or lasting �15 sec with abdominal fetal electrocardiography in throughout any fetal movement during testing effort to clarify FHR pattern and quantitateperiod variability; external monitoring should

continue, and CST or BPP should be doneUnsatisfactory Quality of FHR recording not adequate for Test is repeated in 24 hr or CST is done,

interpretation depending on clinical situation

Reference: Tucker, S. (2004). Pocket guide to fetal monitoring and assessment (5th ed.). St. Louis: Mosby.BPP, Biophysical profile; CST, contraction stress test; FHR, fetal heart rate; NST, nonstress test.


is needed with BPP or CST if the pattern is still nonreactive(Druzin, Gabbe, & Reed, 2002).

Contraction Stress TestThe contraction stress test (CST) is one of the first electronicmethods to be developed for assessment of fetal health. Itwas devised as a graded stress test of the fetus, and its pur-pose was to identify the jeopardized fetus that was stable atrest but showed evidence of compromise after stress. Uter-ine contractions decrease uterine blood flow and placentalperfusion. If this decrease is sufficient to produce hypoxiain the fetus, a deceleration in FHR will result, beginning atthe peak of the contraction and persisting after its conclu-sion (late deceleration).

In a healthy fetoplacental unit, uterinecontractions usually do not produce late decelerations,whereas if there is underlying uteroplacental insuffi-ciency, contractions will produce late decelerations.

The CST provides an earlier warning of fetal compromisethan the NST and with fewer false-positive results. In addi-tion to the contraindications described earlier, the CST ismore time consuming and expensive than the NST. It alsois an invasive procedure if oxytocin stimulation is required.It is infrequently used.

ProcedureThe woman is placed in semi-Fowler position or sits in

a reclining chair with a slight left tilt to optimize uterine per-fusion and avoid supine hypotension. She is monitored elec-tronically with the fetal ultrasound transducer and uterinetocodynamometer. The tracing is observed for 10 to 20 min-utes for baseline rate, long-term variability, and the possibleoccurrence of spontaneous contractions. The two methodsof CST are the nipple-stimulated contraction test and theoxytocin-stimulated contraction test.

Nipple-stimulated contraction test. Severalmethods of nipple stimulation have been described. In oneapproach the woman applies warm, moist washcloths toboth breasts for several minutes. The woman is then askedto massage one nipple for 10 minutes. Massaging the nip-ples causes a release of oxytocin from the posterior pituitary.An alternative approach is for her to massage the nipple for2 minutes, rest for 5 minutes, and repeat the cycles of mas-sage and rest as necessary to achieve adequate uterine activity.When adequate contractions or hyperstimulation (definedas uterine contractions lasting more than 90 seconds or fiveor more contractions in 10 minutes) occurs, stimulationshould be stopped (Druzin, Gabbe, & Reed, 2002).

Oxytocin-stimulated contraction test. Ex-ogenous oxytocin also can be used to stimulate uterine con-tractions. An intravenous (IV) infusion is begun with a scalpneedle. The oxytocin is diluted in an IV solution (e.g., 10units in 1000 ml of fluid), infused into the tubing of themain IV device through a piggyback port, and delivered by

NURSE ALERT

an infusion pump to ensure accurate dosage. One methodof oxytocin infusion is to begin at 0.5 milliunits/min andincrease the dose by 0.5 millunits/min at 15- to 30-minuteintervals until three uterine contractions of good quality areobserved within a 10-minute period. A rate of 10 milli-units/min is usually adequate to elicit uterine contractions(Druzin, Gabbe, & Reed, 2002).

InterpretationIf no late decelerations are observed with the contractions,

the findings are considered negative (Fig. 21-9, A). Repeti-tive late decelerations render the test results positive (Fig. 21-9, B, and Table 21-6).

After interpretation of the FHR pattern, the oxytocin in-fusion is halted, and the maintenance IV solution infused un-til uterine activity has returned to the prestimulation level. Ifthe CST is negative, the IV device is removed, and the fetalmonitor disconnected. If the CST is positive, continued mon-itoring and further evaluation of fetal well-being are indicated.

Nursing Role in AntepartalAssessment for RiskThe nurse’s role is that of educator and support person whenthe woman is undergoing such examinations as ultrasonogra-phy, MRI, CVS, PUBS, and amniocentesis. In some instances,the nurse may assist the physician with the procedure. In manysettings, nurses perform NSTs, CSTs, and BPPs; conduct aninitial assessment; and begin necessary interventions for non-reassuring patterns. These nursing procedures are accomplishedafter additional education and training, under guidance of es-tablished protocols, and in collaboration with obstetricsproviders (Menihan, 2000; Stringer et al., 2003). Patient teach-ing, which is an integral component of this role, involvespreparing the woman for the procedure, interpreting the find-ings, and providing psychosocial support when needed.

Psychologic considerationsAll women who undergo antepartal assessments are at risk

for real and potential problems and may be in an anxiousframe of mind. In most instances, the tests are ordered be-cause of suspected fetal compromise, deterioration of a ma-ternal condition, or both. In the third trimester, pregnantwomen are most concerned about protecting themselves andtheir fetuses and consider themselves most vulnerable to out-side influences. The label of high risk will increase this senseof vulnerability.

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

Women with complicated pregnancies perceive their risksas higher than do women with uncomplicated pregnancies



(Gupton, Heaman, & Cheung, 2001). If the mother has to beplaced on bed rest for pregnancy complications, separationfrom family, finances, and worry about children and home cre-ate further stress (Maloni, Brezinski-Tomasi, & Johnson, 2001).

If the woman is fearful for her own well-being, she maycontinue to feel ambivalence about the pregnancy or maynot accept the reality of the pregnancy. She may not be ableto complete preparations for the baby or go to childbirthclasses if she is on bed rest or hospitalized. The family maybecome frustrated because they cannot engage in these ac-tivities that prepare them for parenthood.

Antepartal hospitalization is an added stressor for the highrisk pregnant woman and her family. The woman may belonely because she is separated from her home and family.She may feel powerless and unable to make decisions for her-self because her care is out of her control. Likewise, prepa-ration for the birth process may be out of control of thewoman and her family. Unexpected procedures and care forthe woman or fetus may take priority over the usual birthplan and may not allow choices that would have been se-lected if the pregnancy had been normal.

Attachment to the newborn can be affected if the motheror newborn is ill after the birth. Early contact may not bepossible. Time, support, and intervention by the health care

team may be necessary to help the family begin the attach-ment process.

The nurse can help the woman and her family regain con-trol and balance in their lives by providing support and en-couragement, providing information about the pregnancyproblem and its management (see Resources list at the endof this chapter), and providing opportunities to make asmany choices as possible about the woman’s care (Coffman& Ray, 2002).

The impact of the effects of a specific pregnancy com-plication and its management is discussed in the followingchapters in this unit.


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Fig. 21-9 Contraction stress test (CST). A, Negative CST. B, Positive CST. (From Tucker, S. [2004].Pocket guide to fetal monitoring and assessment [5th ed.]. St. Louis: Mosby.)

A

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COMMUNITY ACTIVITY

Contact the nearest March of Dimes Birth DefectsFoundation office to assess the resources avail-able for parents (e.g., pamphlets, websites forhigh risk pregnancies) and what screening is rec-ommended during pregnancy to identify prob-lems. How can pregnant women get access tothe March of Dimes information? What informa-tion or resources are available in your communityfor the problems identified?



TABLE 21-6

Guide for Interpretation of the Contraction Stress Test

INTERPRETATION CLINICAL SIGNIFICANCE

NEGATIVE

No late decelerations, with minimum of three uterine con- Reassurance that the fetus is likely to survive labor tractions lasting 40 to 60 sec within 10-min period (see should it occur within 1 wk; more frequent testing may Fig. 21-9, A) be indicated by clinical situation

POSITIVE

Persistent and consistent late decelerations occurring Management lies between use of other tools of fetalwith more than half of contractions (see Fig. 21-9, B) assessment such as BPP and termination of pregnancy

(e.g., labor induction, cesarean birth); a positive test re-sult indicates that fetus is at increased risk for perinatalmorbidity and mortality; physician may perform expe-ditious vaginal birth after successful induction or mayproceed directly to cesarean birth; decision to inter-vene is determined by fetal monitoring and presenceof FHR reactivity

SUSPICIOUS

Late decelerations occurring in less than half of uterine con- NST and CST should be repeated within 24 hr; if inter-tractions once adequate contraction pattern established pretable data cannot be achieved, other methods of fe-

tal assessment must be used*

HYPERSTIMULATION

Late decelerations occurring with excessive uterine activity (contractions more often than every 2 min or lasting �90 sec) or persistent increase in uterine tone

UNSATISFACTORY

Inadequate uterine contraction pattern, or tracing too poor to interpret

Reference: Tucker, S. (2004). Pocket guide to fetal monitoring and assessment (5th ed.). St. Louis: Mosby.BPP, Biophysical profile; CST, contraction stress test; FHR, fetal heart rate; NST, nonstress test.*Applies to results noted as suspicious, hyperstimulation, or unsatisfactory.

• A high risk pregnancy is one in which the life orwell-being of the mother or infant is jeopardizedby a biophysical or psychosocial disorder coinci-dental with or unique to pregnancy.

• Biophysical, sociodemographic, psychosocial,and environmental factors place the pregnancy andfetus or neonate at risk.

• Psychosocial perinatal warning indicators includecharacteristics of the parents, the child, their sup-port systems, and family circumstances.

• Maternal and perinatal mortality rates for Cau-casians are considerably lower than for other eth-nic groups in the United States.

• Mortality rate decreases when risk is identifiedearly and intensive care is applied.

• Biophysical assessment techniques include fetalmovement counts, ultrasonography, and MRI.

• Biochemical monitoring techniques include am-niocentesis, PUBS, CVS, and MSAFP.

• Reactive NSTs and negative CSTs suggest fetalwell-being.

• Most assessment tests have some degree of riskfor the mother and fetus and usually cause someanxiety for the woman and her family.

Key Points

Down Syndrome1 Yes, there is sufficient evidence about use of ultrasound in the

first trimester to obtain information about the pregnancy otherthan detecting fetal anomalies.

2 a. There is an increased risk of having a child with Down syndrome with increased maternal age, especially after age 40. For example, the incidence is 1 in 400 at age 35 and 1 in30 at age 45.

Answer Guidelines to Critical Thinking Exercise



Healthy Mothers, Healthy Babies Coalition409 12th St., SWWashington, DC 20024202-863-2458

March of Dimes Birth Defects FoundationNational Foundation/March of Dimes1275 Mamaroneck Ave.White Plains, NY 10605914-428-7100888-663-4637 (MODIMES)www.modimes.org

National Clearinghouse for Human Genetic Disease (providesinformation about inherited diseases)

National Center for Education in Maternal and Child Health38th and R Sts., NWWashington, DC 20057

National Institute of Child Health and Human Development(NICHD)

National Institutes of Health9000 Rockville PikeBldg. 31, Room 2A32Bethesda, MD 20892301-496-4000www.nih.gov

Parenthood after Thirty451 VermontBerkeley, CA 94707415-524-6635

Spina Bifida Association of America4590 McArthur Blvd., NW, Suite 250Washington, DC 20007-4226800-621-3141

Resources

Alfirevic, Z., Sundberg, K., & Brigham, S. (2003). Amniocentesis andchorionic villi sampling for prenatal diagnosis. (Cochrane Re-view). In The Cochrane Library, Issue 4, 2005. Chichester, UK: JohnWiley & Sons.

American Academy of Pediatrics (AAP) & American College of Ob-stetricians and Gynecologists (ACOG). (2002). Guidelines for perinatalcare (5th ed.). Elk Grove Village, IL: AAP & ACOG.

American College of Obstetricians and Gynecologists (ACOG). (2004).ACOG issues position on first-trimester screening methods. News release.Internet document available at www.acog.org/from_home/publications/press_releases/nr06-30-04.cfm (accessed January 6, 2005).

Arias, E., MacDorman, M., Strobino, D., & Guyer, B. (2003). Annualsummary of vital statistics—2003. Pediatrics, 112(6 Pt 1), 1215-1230.

Association of Women’s Health, Obstetric and Neonatal Nurses(AWHONN). (1998). Nursing practice competencies and educationalguidelines for limited ultrasound examination in obstetric and gynecol-ogy/infertility settings (2nd ed.). Washington, DC: AWHONN.

Athey, P., & Hadlock, F. (1985). Ultrasound in obstetrics and gynecology(2nd ed.). St. Louis: Mosby.

Benn, P., Egan, J., Fang, M., & Smith-Bindman, R. (2004). Changes inutilization of prenatal diagnosis. Obstetrics & Gynecology, 103(6), 1255-1260.

Chervenak, F., & Gabbe, S. (2002). Obstetric ultrasound: Assessmentof fetal growth and anatomy. In S. Gabbe, J. Niebyl, & J. Simpson(Eds.), Obstetrics: Normal and problem pregnancies (4th ed.). New York:Churchill Livingstone.

Coffman, S., & Ray, M. (2002). African American women describe sup-port processes during high-risk pregnancy and postpartum. Journalof Obstetric, Gynecologic, and Neonatal Nursing, 31(5), 536-544.

Druzin, M., Gabbe, S., & Reed, K. (2002). Antepartum fetal evaluation.In S. Gabbe, J. Niebyl, & J. Simpson (Eds.), Obstetrics: Normal andproblem pregnancies (4th ed.). New York: Churchill Livingstone.

Enkin, M., Keirse, M., Neilson, J., Crowther, C., Duley, L., Hodnett,E., & Hofmeyr, G. (2001). Effective care in pregnancy and childbirth:A synopsis. Birth, 28(1), 41-51.

Fanaroff, A., Martin, J., & Rodriguez, R. (2004). Identification and man-agement of problems in the high-risk neonate. In R. Creasy, R. Resnik, & J. Iams (Eds.), Maternal-fetal medicine: Principles and prac-tice (5th ed.). Philadelphia: Saunders.

Garcia, J., Bricker, L., Henderson, J., Martin, M., Mugford, M., Neil-son, J., & Roberts, T. (2002). Women’s views of pregnancy ultra-sound: A systematic review. Birth, 29(4), 225-247.

Gilbert, E., & Harmon, J. (2003). Manual of high risk pregnancy and de-livery (3rd ed.). St. Louis: Mosby.

References

b. Ultrasound is used in the first trimester for determining sizeand number of fetuses, presence of fetal cardiac and bodymovements, presence of uterine abnormalities, dating preg-nancy, and identifying the presence and location of an in-trauterine device (IUD). Fetal anomalies may be detected inthe second trimester.

c. The triple-screen test—maternal serum alpha-fetoprotein(MSAFP), uncongugated estriol, and beta-human chorionicgonadotropin (�-hCG)—at 16 to 18 weeks may predict up to60% of cases of Down syndrome, although follow-up diag-nostic testing with amniocentesis is needed to confirm thediagnosis. Lower-than-normal MSAFP and unconjugated es-triol levels and elevated �-hCG levels in the second trimesterare associated with Down syndrome.

3 The priority is to teach Patty what information the ultrasoundexamination at 8 weeks will provide. Information about otheroptions (e.g., chorionic villus sampling [CVS]) to identify Downsyndrome in the first trimester and the screening tests availablein the second trimester may also be appropriate.

4 Yes, there is sufficient evidence to support this conclusion.5 After hearing the choices, Patty and David may decide to have

a CVS done or may wait until the second trimester for screen-ing tests and then have amniocentesis if the screening tests war-rant follow-up. They may also wait for a second-trimester ul-trasound examination.


Gillem-Goldstein, J. et al. (2003). Methods of assessment for pregnancyat risk. In A. DeCherney, & L. Nathan (Eds.), Current obstetric andgynecologic diagnosis and treatment (9th ed.). New York: Lange Med-ical Books/McGraw-Hill.

Glantz, J., & Woods, J. (2004). Significance of amniotic fluid meco-nium. In R. Creasy, R. Resnik, & J. Iams (Eds.), Maternal-fetal med-icine: Principles and practice (5th ed.). Philadelphia: Saunders.

Gordon, M. (2002). Manual of nursing diagnosis (10th ed.). St. Louis:Mosby.

Gupton, A., Heaman, M., & Cheung, L. (2001). Complicated and un-complicated pregnancies: Women’s perception of risk. Journal of Ob-stetric, Gynecologic, and Neonatal Nursing, 30(2), 192-201.

Harman, C. (2004). Assessment of fetal health. In R. Creasy, R. Resnik,& J. Iams (Eds.), Maternal-fetal medicine: Principles and practice (5th ed.).Philadelphia: Saunders.

Jenkins, T., & Wapner, R. (2004). Prenatal diagnosis of congenital dis-orders. In R. Creasy, R. Resnik, & J. Iams (Eds.), Maternal-fetal med-icine: Principles and practice (5th ed.). Philadelphia: Saunders.

Kochanek, K., Murphy, S., Anderson, R., & Scott, C. (2004). Deaths:Final data for 2002. National Vital Statistics Reports, 53(5), 1-115.

Maloni, J., Brezinski-Tomasi, J., & Johnson, L. (2001). Antepartum bedrest: Effect upon the family. Journal of Obstetric, Gynecologic, andNeonatal Nursing, 30(2), 67-77.

Manning, F. (2004). General principles and applications of ultrasound.In R. Creasy, R. Resnik, & J. Iams (Eds.), Maternal-fetal medicine: Prin-ciples and practice (5th ed.). Philadelphia: Saunders.

Menihan, C. (2000). Limited ultrasound in nursing practice. Journal ofObstetric, Gynecologic, and Neonatal Nursing, 29(3), 325-330.

Parer, J., & Nageotte, M. (2004). Intrapartum fetal surveillance. In R. Creasy, R. Resnik, & J. Iams (Eds.), Maternal-fetal medicine: Prin-ciples and practice (5th ed.). Philadelphia: Saunders.

Ramer, L., & Frank, B. (2001). Pregnancy: Psychosocial perspectives (3rd ed.).White Plains, NY: March of Dimes Birth Defects Foundation.

Silbergeld, E. & Patrick, T. (2005). Environmental exposures, toxico-logic mechanisms, and adverse pregnancy outcomes. American Jour-nal of Obstetrics and Gynecology, 192(5), S11-121.

Simpson, J. (2002). Genetic counseling and prenatal diagnosis. In S. Gabbe, J. Niebyl, & J. Simpson (Eds.), Obstetrics: Normal and prob-lem pregnancies (4th ed.). New York: Churchill Livingstone.

Stringer, M., Miesnik, S., Brown, L., Menei, L., & Macones, G. (2003).Limited obstetric ultrasound examinations: Competency and cost.Journal of Obstetric, Gynecologic, and Neonatal Nursing, 32(3), 307-312.

Tan, K., & Sabapathy, A. (2001). Maternal glucose administration forfacilitating tests of fetal wellbeing (Cochrane Review). In The CochraneLibrary, Issue 4, 2005. Chichester, UK: John Wiley & Sons.

Tan, K., & Smyth, R. (2001). Fetal vibroacoustic stimulation for facil-itation of tests of fetal wellbeing (Cochrane Review). In The CochraneLibrary, Issue 4, 2005. Chichester, UK: John Wiley & Sons.

Tucker, S. (2004). Pocket guide to fetal monitoring and assessment (5th ed.).St. Louis: Mosby.

United States Department of Health and Human Services (USDHHS).(2000). Healthy People 2010. (Conference Edition) (Vol. 1-2). Wash-ington, DC: U.S. Government Printing Office.

Wilson, R. (2000). Amniocentesis and chorionic villus sampling. Cur-rent Opinion in Obstetrics and Gynecology, 12(2), 81-86.



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