Antepartum fetal testing

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Antepartum Fetal testingM. Kamil

Antepartum - occurring before childbirth


Goals of antepartum fetal testingTo assess fetal well-being and prediction of future fetal condition

To prevent/ identify fetuses at riskIntrauterine death (IUD)Complications of intrauterine asphyxia

For early intervention to prevent IUD or complication of IU asphyxia

Look for fetal healthIdentify fetuses at risk of IUD.Identify fetuses at risk of other complications of IU asphyxia and intervene to prevent these adverse outcomes.


TestsSubjective maternal perception of fetal activityFetal movement counting

Objective testsNon stress test (NST)Contraction stress test (CST)Biophysical profile (BPP)Umbilical artery blood flow velocity

Number of movements each day/ Contraction stress test (CST) or they called Oxytocin challenge test (OCT) if oxytocin is used


Diabetes Pregestational diabetes, gestational diabetes treated with anti-hyperglycemic drugs, or gestational diabetes poorly controlled with nutritional therapy aloneHypertensive disordersFetal growth restrictionTwin pregnancyPostterm pregnancyDecreased fetal activitySystemic lupus erythematosusAntiphospholipid syndromeSickle cell diseaseAlloimmunizationOligohydramnios or polyhydramniosPrior fetal demisePreterm premature rupture of membranesOther Nonimmune hydrops, maternal cyanotic heart disease, poorly controlled maternal hyperthyroidism, and maternal vascular diseases are associated with an increased risk of fetal demise and generally considered appropriate indications for antenatal fetal testing.


1. Fetal movement countingClinically important parameter of fetal wellbeing


Assessed by mother subjectively

Number of movements kick counts/ hour

Cardif count 10 formulaThe pt is instructed to report if:< 10 mvmt occur during 12 hours on 2 consecutive daysNo mvmt perceived even after 12 hours in a single day

Fetal movement countingObjective maternal assessment of fetal movements is based on evidence that fetal movement decreases in response to hypoxemia

Maternal perception of fetal movement typically begins in the second trimester at around 16 to 20 weeks of gestation.

Indirect measure of CNS integrity and function.5

Can start at 24 weeks. Before that useless.Diabetid: start surveillance at 32 weeks.


2. Non stress test (NST)Study the response of FHR to fetal movements.


Normal/Reactive/Reassuringif there are two accelerations of the FHR in 20 minutes that are at least 15 beats above the baseline heart rate and last for at least 15 seconds (Blueprint 8)1 small boxes is 10 sec. At least 2 small boxesUsually performed after 30 weeks after fetal NS maturation

Non reactive cause by interrupted fetal oxygenation to the point of metabolic academia

Also cause by fetal immaturity, quiet fetal sleep, maternal smoking (women who smoke should not smoke proximate to an NST), fetal neurologic or cardiac anomalies, sepsis, or maternal ingestion of drugs with cardiac effects [30]. Sleep is a common and benign cause of nonreactivity

FHR = Fetal heart rate7

Non stress test: Prep

Contraction stress testThe contraction stress test (CST) is based on the fetal response to a transient reduction in fetal oxygen delivery during uterine contractions. If the fetus becomes hypoxemic (fetal arterial pO2 below 20 mm Hg [16,17]), fetal chemoreceptors and baroreceptors, as well as sympathetic and parasympathetic influences, respond by reflex slowing of the fetal heart rate (FHR), which may manifest clinically as late decelerations (waveform 1 and waveform 2). Performance of the CST, as well as its interpretation and use, are described in detail separately.

The CST is seldom performed given the wide availability of other tests (eg, nonstress test, biophysical profile) that dont have its drawbacks. Major drawbacks related to use of the CST include the need to stimulate contractions with intravenous oxytocin, the contraindication to inducing contractions in some conditions (eg, placenta previa), and the high false-positive rate (ie, fetus goes on to tolerate labor without FHR changes necessitating intervention). In contrast, the false-negative rate (ie, rate of antepartum stillbirth within one week of a negative test) is very low (table 1), thus providing reassurance of adequate fetal oxygenation after a normal test result8

Non stress test: ResultNormal/R2 accelerations of the FHR in 20 minAt least 15 beats above the baseline HRLast for at least 15 secondsAbnormal/NRNo FHR accelerations over a 40 min periodPresence of decelerations with fetal movement


Non-stress test: Example

12 minutes strip


Abnormal resultsAbsence of accelerations does not predict fetal compromise.Fetus may not move for periods up to 75 minutesSo need to consider longer duration of Nonstress test up to 120 minSleeping fetusAbnormal test can revert to normal as feta; condition changes, vice versaHammacher and coworkers described tracings with what they term a silent oscillatory pattern that he considered dangerous.FHR that oscillated less than 5 bpm and presumably indicated absent acceleration and beat-to-beat variability.Terminal cardiotocogram (CTG)Baseline oscillation of less than 5 bpmAbsent of accelerationLate decal with spontaneous uterine contractionAssociated withUteroplacental pathologyFetal-growth restrictionOligohydramniosFetal academiaMeconiumPlacental infarction

Normal test can become abnormal if fetal condition deteriorates11

Interval between testingUsually 7 days.More frequents testing for high risk. Perform twice-weekly with additional testing completed for maternal or fetal deterioration regardless of the time elapsed since the last test.Postterm pregnancyMultifetal gestationT1DMFetal-growth restrictionGestational hypertensionSome perform daily or even more freqSevere preeclampsia remote from term

variable decelerations, if nonrepetitive and briefless than 30 secondsdo not indicate fetal compromise or the need for obstetrical intervention

repetitive variable decelerationsat least three in 20 minuteseven if mild, have been associated with an increased risk of cesarean delivery for fetal distress

Decelerations lasting 1 minute or longer have been reported tohave an even worse prognosis


3. Contraction Stress TestMeasure fetal response to a transient reduction in fetal oxygen delivery during uterine contractions

Induce with Nipple stimulationInfusion of dilute oxytocin solution 0.5 mU/min


CTGPut transducers for a baseline tracing for 10 to 20 minutesIf at least 3 spontaneous contraction of 40 sec or longer are present in 10 min, no uterine stimulation is necessary.If there is fewer than 3 contraction in 10 min -> do uterine stimulation.Start with nipple stimulation by rubbing the one nipple tru her clothing for 2 min. or until contraction begin. If not after 5 min interval, retry nipple stimulation to schieve the desired pattern. If unsuccessful induce uterine contractions

This test generally repeated on a weekly basis, and the investigators concluded that negative contraction stress results, that is normal results, shows fetal is healthy.If positive/+ = Also suggestive cord compression, suggesting oligohydramnios, which is often a concomitant of placental insufficiency.

Disadv: Req 90 min to complete.

n weekly basis13

CST: Interpretation

Cunningham, F., & Williams, J. (2014). Williams obstetrics. (24th ed. / [edited by] F. Gary Cunningham et al. ed.). New York ; London: McGraw-Hill Medical.NormalAbnormal

If have late decelerations = uteroplacental insufficiency14

4.Biophysical profile (BPP)More accurate.Consist 5 assessments

Cunningham, F., & Williams, J. (2014). Williams obstetrics. (24th ed. / [edited by] F. Gary Cunningham et al. ed.). New York ; London: McGraw-Hill Medical.

More accurate for assessing fetal health than single element.tests require 30 to 60 minutes of examiner time.biophysical test scores were higher if a testwas performed in late evening (8 to 10 pm) compared with 8 to 10 am.

biophysical score of 0 was almost invariablyassociated with significant fetal acidemia, whereas a normalscore of 8 or 10 was associated with normal pH

An equivocaltest resulta score of 6was a poor predictor of abnormaloutcome. As the abnormal score decreased from 2 or 4 downto a very abnormal score of zero, this was a progressively moreaccurate predictor of abnormal fetal outcome.


Fetal breathingCharacteristic: Paradoxical chest wall movement

Cunningham, F., & Williams, J. (2014). Williams obstetrics. (24th ed. / [edited by] F. Gary Cunningham et al. ed.). New York ; London: McGraw-Hill Medical.

Suggested that fetal respiratory rate decreased in conjunction with increase respiratory volume at 33 36 weeks and coincidental with lung maturityCan be visualize by ultrasound.Factor affecting fetal resp. mvmt hypoglycemia, sound stimuli, cigar smoking, amniocentesis, impeding preterm laborShould perform 24 hour observation using U/S to char fetal breathing patterns during the last weeks of pregnancy16

Interpretation of BPP

Cunningham, F., & Williams, J. (2014). Williams obstetrics. (24th ed. / [edited by] F. Gary Cunningham et al. ed.). New York ; London: McGraw-Hill Medical.

Amniotic fluid volumeIn the hy