Chapter 10: Antepartum Fetal Assessment

Question 1

why is an antepartum fetal assessment done?

Answer 1

• to detect congenital anomalies and evaluate the condition of the fetus
• but no antepartal testing or antepartal surveillance procedure can guarantee the birth of a perfect infant

Question 2

role of perinatal nurses in antepartal fetal assessments

Answer 2

• be prepared to offer clear explanations of diagnostic procedures and any problems the woman should report
• support for the family requiring fetal diagnostic tests can reduce their anxiety

Question 3

antepartum fetal assessment

Answer 3

• Each is an assessment to measure the presence or absence of fetal well being
• Potentially only for indications
• Some are within the scope of nursing practice to do
  
  • Some are not, but a nurse is expected to participate in procedure and/or provide patient education

Question 4

goals of antepartum fetal assessment

Answer 4

• determine fetal health or compromise accurately
• reduce perinatal morbidity and mortality
• guide intervention by the OB team

Question 5

ultrasound

Answer 5

• can provide 2D or 3D imaging
• real time so able to observe fetal heart motion, fetal breathing, fetal movement
• can be done transabdominally or transvaginally

Question 6

levels of ultrasound

Answer 6

• standard (basic): general survey of fetus, placenta, and amniotic fluid volume
• specialized (comprehensive): done if abnormalities found during basic scan
• limited: done to address placental location, fetal cardiac activity, determine presentation, assess volume of amniotic fluid

Question 7

first trimester ultrasonography

Answer 7

• most used to:
  
  • confirm pregnancy
  • verify location of pregnancy and identify multifetal gestation
  • determine gestation age
  • determine location of uterus, cervix, placenta for chorionic villus sampling (CVS)
• crown rump (CRL) measurement is most reliable measurement of gestational age
• viability confirmed by fetal heartbeat which is visible when CRL is 5 mm

Question 8

second and third trimester ultrasonography

Answer 8

• usually transabdominal
• purposes:
  
  • confirm viability
  • evaluate anatomy
  • confirm gestational age
  • assess fetal growth
  • locate placenta
  • determine preseantation
• becomes more difficult to evaluate gestational age, but need accurate fetal age if assessing alpha getoprotein levels or looking at IUGR

Question 9

advantages of ultrasound

Answer 9

• shows clear visibility of the fetus and surrounding structures
• has been proven safe
• noninvasive
• comfortable
• results are immediate
• portable and available

Question 10

disadvantages of ultrasound

Answer 10

• cost
• if don’t get an ultrasound during 1st trimester, gestational age will not be calculated as accurately
• cannot identify all defects of fetal structure or function
• possible anxiety for new parents if abnormal results are found

Question 11

dopper ultrasound

Answer 11

• used when pregnancies are complicated by HTN or fetal growth restriction to identify abnormalities in blood flow

Question 12

alpha fetoprotein screening

Answer 12

• AFP is the predominant protein in the fetal plasma
• it diffuses from fetal plasma to fetal urine to the amniotic fluid
  
  • some crosses the placenta, so it can be measured in maternal blood (MSAFP) or in amniotic fluid (AFAFP)
• low levels of MSAFP suggest chromosomal abnormalities, like trisomy 21
• elevated levels of MSAFP suggest neural tube defects like anencephaly or spina bifida
• done b/w 16 and 18 weeks gestation
• can be affected by gestational age, maternal weight, multifetal pregnancy, race, maternal diabetes, and ethnicity

Question 13

advantages of MSAFP evaluation

Answer 13

• simple
• not invasive to fetus
• economic
• early screening so allows time for more comprehensive screening if it comes back abnormal

Question 14

limitations of MSAFP evaluation

Answer 14

• screening test, not diagnostic
• benign conditions such as inaccurate estimation of gestational age can result in apparently abnormal levels in a health fetus
• timing: can only be done b/w 16-18 weeks
• normal levels of AFP do not guarantee that the baby is free of structural defects

Question 15

multiple marker screening

Answer 15

• test for hCG and unconjugated estriol (along with MSAFP): triple screen
  
  • inc detection of trisomy 18 and 21, so noninvasive test for NTD
• samples taken b/w 16-18 weeks, and are considered positive for an anomaly if MSAFP and estriol are low and hCG is high
• quad screen: adds placental inhibin A which will help improve screening of trisomy 21 in women under 35

Question 16

chorionic villus sampling (CVS)

Answer 16

• the villi are fetal tissues that are projections of the outer membrane that burrow into endometrial tissue–>they have the chromosomal, metabolic, and genetic makeup of the fetus
• performed b/w 10-12 weeks
• must include genetic counseling about the specific defect which the CVS is being performed
• can be done by transcervical or transabdominal approach
• after CVS, fetal heart activity is documented to confirm viability
  
  • maternal V/S are assessed
  • RhoGAM is given if women is Rh negative
  • small amount of vaginal bleeding may occur, need to rest at home and avoid sex for a few days

Question 17

advantages of CVS

Answer 17

• results are known early
• offers prenatal diagnosis early in pregnancy
• if a woman chooses abortion based on the results, it may be less physically and emotionally traumatic than a later procedure

Question 18

risks of CVS

Answer 18

• fetal loss
• limb reduction defects
• preliminary results available w/in 2-3 hours, but they are incubated for 2-4 days after
  
  • if questionable results, may require a more expensive and invasive amniocentesis

Question 19

amniocentesis

Answer 19

• done b/w 15-20 weeks b/c of the need for adequate fluid volume and quantity of viable fetal cells
• complication: foot deformation (clufoot)
• if done in midtrimester: for chromosomal abnormalities, to diagnose intrauterine infections, maternal Rh sensization
  
  • if done in early pregnancy, must be done with a full bladder
• if done in 3rd trimester: to determine fetal lung maturity and evaluate the fetal condition when the woman has Rh isoimmunization
  
  • if done in late pregnancy, done with an empty bladder
• maternal BP and FHR are assessed prior to amniocentesis
  
  • after: assess FHR and use ultrasound to verify reassuring FHR and amount of fluid
  • RhoGAM is administered to Rh negative women

Question 20

test to determine fetal lung maturity

Answer 20

• done with amniocentesis when delivery is considered before 38 full weeks gestation
• lecithin/sphingomyelin (L/S) ratio is a test for estimating fetal lung maturity
  
  • they are present in equal amounts until 30 weeks gestation, but at a ratio of at least 2:1, then there should be adequate surfactant and mature fetal lungs
  • also test for phosphatidylglycerol (PG) and phosphatidylinositol (PI) which are components of surfactant

Question 21

test for fetal hemolytic disease

Answer 21

• done with an amniocentesis
• used to determine fetal bilirubin concentration with deltaOD450 test to measure optical density of the amniotic fluid stained by bilirubin if the mother is Rh neg and was sensitized after being exposed to Rh+ blood

Question 22

advantages of amniocentesis

Answer 22

• simple and reasonably safe
• painless
• few reported complications

Question 23

disadvantages and risks of amniocentesis

Answer 23

• disadvantages:
  
  • timing
    
    • done later in pregnancy, so may give woman little to to terminate before 20 weeks
• risks:
  
  • pregnancy loss
    
    • ultrasound guidance helps prevent the placenta or cord being pierced
  • transfer of fetal blood to maternal circulation

Question 24

percutaneous umbilical blood sampling

Answer 24

• “PUBS”: involves aspiration of fetal blood from the umbilical cord for prenatal diagnosis or therapy
• indications: diagnosis and management of Rh disease, diagnosis of abnormal blood clotting, and determination of acid base status of the fetus
• use ultrasound to guide needle insertion
  
  • umbilical vein is more commonly used b/c it is larger
    
    • need to know which vessel is sampled for acid base analysis
• FHR is monitored electronically for 30-60 min after
• RhoGAM is administered

Question 25

risk of PUBS

Answer 25

• fetal bradycardia
  
  • sometimes can be severe if puncture the umbilical artery
• prolonged bleeding from cord
• cord laceration
• cord hematoma
• thrombosis
• thromboembolism
• preterm labor
• premature ROM
• maternal blood sensitization

Question 26

nonstress test

Answer 26

• helps identify whether an inc in the FHR occurs when fetus moves which indicates adequate oxygenation, healthy neural pathway, and ability of heart to respond to stimuli
  
  • if it doesn’t accelerate, fetal hypoxemia and acidosis are concerns
• can help identify intraamniotic infections if membranes rupture prematurely
• involves 40 min of electronic fetal monitoring
• called non stress b/c just observation, so not challeneged or stressed under uterine contractions
• before test:
  
  • woman should void and baseline V/S taken
  • HOB elevated to at least 45 deg
• use transducers and the woman presses a button each time she feels fetal movemnt
• interpreted by physician:
  
  • reassuring or reactive: at least 2 heart accelerations occur w/in a 20 min period, peak at least 15 bpm above baseline and last at leat 15 sec

Question 27

advantages and disadvantage of a NST

Answer 27

• advantages:
  
  • noninvasive
  • painless
  • no risk to mom or fetus
  • fetal surveillance if pregnancy has uteroplacental insufficiency
  • immediate results
• disadvantages:
  
  • false positive test
    
    • vibroacoustic stimulation can redce these
  • sleep is often cause of lack of fetal movement

Question 28

vibroacoustic stimulation (VAS)

Answer 28

• uses sound stimulation to elicit fetal movement
  
  • can be used with a NST
• reactive test results can predict fetal well being
• applied over maternal abdomen at fetal head: can be repeated at 1 min intervals up to 3 times
• brain responses in fetus to auditory stimulation appear at 26-28 weeks
• appears to be safe

Question 29

contraction stress test

Answer 29

• can be done if NST is nonreactive
• CST records the response of FHR to uterus induced by uterine contractions, identifying the fetus whose O2 reserves are insufficient to tolerate recurrent mild hypoxia or uterine contractions
• variability and accelerations are reassuring
• contraindications: preterm labor, preterm ROM, hx of extensive uterine surgery or classical C/S incision, placenta previa
• woman lies in semi fowler’s
  
  • check if already having at least 3 contractions in 10 min window lasting 40 sec, but if not, then have to induce contractions w/ either nipple stimulation (to secrete oxytocin) or IV piggy back oxytocin w/ LR

Question 30

CST interpretation

Answer 30

• negative (normal/reassuring): no late decels, although the fetus is stressed by at least 3 contractions w/in 10 min at least 40 sec long
• positive (abnormal/nonreassuring): late decels accompany at least 50% of contractions, even when fewer than 3 contractions in 10 min
• equivocal (suspicious): intermittent late decels and significant variable decels
• equivocal (hyperstimulation): FHR decels occurring in presence of contractions that are closer than Q2 min or longer than 90 sec
• unsatisfactory: fewer than 3 contractions in 10 min

Question 31

advantages of CST

Answer 31

• minimally invasive
• if negative, then CST offers more than 99% reassurance that uteroplacental urit can support life for at least 1 more week
• positive CST allows physician to analyze options and make a birth plan

Question 32

disadvantages of CST

Answer 32

• more time consuming than NST
• requires precision to get adequate contraction pattern
• cost is higher, esp if use oxytocin

Question 33

biophysical profile (BPP)

Answer 33

• assess: FHR, fetal breathing movements, fetal gross movements, fetal muscle tone, and amniotic fluid volume
• evaluate both acute (FHR (w/ NST), fetal breathing movements (US), fetal gross movements (US), fetal muscle tone (US)) and chronic (amniotic fluid volume (US)) components
• scored from 0-10
  
  • 10 is perfect, 0 is worst
  • 8-10 is considered normal unless oligohydramnios is present which may indicate chronic hypoxia

Question 34

what are the effects of gradual hypoxemia and worsening fetal pH?

Answer 34

• loss of FHR reactivity
• reduced, then absent fetal breathing movements
• reduced, then absent gross fetal movements
• reduced fetal tone
• prolonged hypoxemia: reduced amniotic fluid volume

Question 35

maternal assess of fetal movement

Answer 35

• assessed by the mother and often called “kick counts”
• inc fetal movement is a reassuring sign of fetal well being
• most often perceived when lying on their left side
• assess by instructing the woman to lie on side with hands on largest part of abdomen, concentrate, and record number of movements
• influences on activity:
  
  • sleep/wake cycles
  • maternal activity
  • obesity
  • sound
  • blood glucose
  • time of day

Question 36

advantages of kick counting

Answer 36

• free
• noninvasive
• may identify fetal problems early in the client who has no known risk factors
• convenient and validates her perceptions of fetal status

Question 37

disadvantages of kick counting

Answer 37

• fetal resting state decreases movements
• maternal perception of movement may vary
• time of day may affect fetal movement (lower in the morning, higher in the evening)
• drugs taken by mother (methadone, heroin, cocaine, alcohol, tobacco)
• mother may evaluate fetal movements erratically, making counts less informative