Ante Part Um Fetal Assesment

8/2/2019 Ante Part Um Fetal Assesment

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FETAL MOVEMENTS FETAL BREATHING

CONTRACTION STRESS TESTING

NONSTRESS TESTS BIOPHYSICAL PROFILE

AMNIONIC FLUID VOLUME

DOPPLER VELOCIMETRY


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the goals of antepartum fetal surveillance includeprevention of fetal death and avoidance ofunnecessary interventions.

In most cases, a negative, that is, normal testresult is highly reassuring, because fetal deaths

within 1 week of a normal test are rare. Indeed, negative-predictive valuesa true

negative testfor most of the tests described are99.8 percent or higher.

In contrast, estimates of the positive-predictive

valuesa true positive testfor abnormal testresults are low and range between 10 and 40percent.


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Passive unstimulated fetal activitycommences as early as 7 weeks.

An important determinant of fetal activityappears to be sleep-awake cycles, which areindependent of the maternal sleep-awakestate.

Sleep cyclicity has been described as varying

from about 20 minutes to as much as 75minutes.


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Normal weekly maternal counts of fetalmovements ranged between 50 and 950, withlarge daily variations that included counts aslow as 4 to 10 per 12-hour period in normal

pregnancies.

The perception of 10 distinct movements inup to 2 hours is considered reassuring.

The counting can be discontinued for thatday after 10 movements.


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Paradoxical chest wall movement. One interpretation of the paradoxical

respiratory motion might be coughing toclear amnionic fluid debris.

Although the physiological basis for thebreathing reflex is not completelyunderstood, such exchange of amnionic fluid

appears to be essential for normal lungdevelopment.

Added as a part of biophysical profile


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The criterion for a positive (abnormal) test wasuniform repetitive late fetal heart ratedecelerations. These reflected the uterinecontraction waveform and had an onset at orbeyond the acme of a contraction.

Such late decelerations could be the result ofuteroplacental insufficiency. The tests weregenerally repeated on a weekly basis, and theinvestigators concluded that negative (normal)contraction stress tests forecast fetal health.

One disadvantage cited was that the averagecontraction stress test required 90 minutes tocomplete.


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Criteria for Interpretation of the Contraction(Stress Test) Negative: no late or significant variable decelerations Positive: late decelerations following 50% or more of

contractions (even if the contraction frequency is fewer

than three in 10 minutes) Equivocal-suspicious: intermittent late decelerations or

significant variable decelerations Equivocal-hyperstimulatory: fetal heart rate

decelerations that occur in the presence of contractions

more frequent than every 2 minutes or lasting longerthan 90 seconds Unsatisfactory: fewer than three contractions in 10

minutes or an uninterpretable tracing


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Fetal heart rate and uterine contractions are recordedsimultaneously with an external monitor. If at leastthree spontaneous contractions of 40 seconds orlonger are present in 10 minutes, no uterinestimulation is necessary .

Contractions are induced with either oxytocin ornipple stimulation if there are fewer than three in 10minutes. If oxytocin is preferred, a dilute intravenousinfusion is initiated at a rate of 0.5 mU/min anddoubled every 20 minutes until a satisfactory

contraction pattern is established Nipple stimulation to induce uterine contractions is

usuallysuccessful for contraction stress testing.


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Beat to beat variability (autonomic) Pathological loss of acceleration may be seen

in conjunction with significantly decreasedbeat-to-beat variability of the fetal heart rate.

Most commonly associated with sleep cycles,It also may be caused by central depressionfrom medications or maternal cigarette

smoking. Acceleration (movements)


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Observation of a decrease in the number ofaccelerations in preterm fetuses subsequentlyfound to have lower umbilical artery blood PO2values.

Abnormal NST (1) baseline oscillation of less than 5 bpm, (2) absent accelerations. (3) late decelerations with spontaneous uterine

contractions.

Fetal-growth restriction in 75 percent,

oligohydramnios in 80 percent, fetal acidosis in40 percent, meconium in 30 percent, andplacental infarction in 93 percent.


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It was shown that 60 to 70 percent of thesmall placental arterial channels would needto be obliterated before the umbilical arteryDoppler waveform became abnormal.

Such extensive placental vascular pathologyhas a major effect on the fetal circulation.


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Because more than 40 percent of the combined fetalventricular output is directed to the placenta,obliteration of vascular channels in the placental-umbilical circulation increases afterload and leads tofetal hypoxemia.

This in turn leads to dilatation and redistribution ofmiddle cerebral artery blood flow. Ultimately,pressure rises in the ductus venosus due to afterloadin the right side of the fetal heart.

Thus, it is postulated that such placental vasculardysfunction results in increased umbilical artery

blood flow resistance, which progresses to decreasedmiddle cerebral artery impedance followed ultimatelyby abnormal flow in the ductus venosus (chronichypoxemia)


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The utility of umbilical artery Doppler velocimetrywas reviewed by the American College ofObstetricians and Gynecologists (2000, 2004). Itwas concluded that no benefit has beendemonstrated other than in pregnancies with

suspected fetal growth restriction. Specifically, no benefits have been demonstrated

for velocimetry for other conditions such aspostterm pregnancy, diabetes, systemic lupuserythematosus, or antiphospholipid antibody

syndrome. Similarly, velocimetry has not proved of value as

a screening test for detecting fetal compromisein the general obstetrical population.


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Doppler velocimetry interrogation of themiddle cerebral artery (MCA) has receivedparticular attention because of observationthat the hypoxic fetus attempts brain sparing

by reducingcerebrovascular impedance andthus increasing blood flow.

(no significant differences in pregnancyoutcomes between patients were followed byeither biophysical profile vs. MCA)


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Negative or reversed flow in the ductusvenous was a late finding because thesefetuses had already sustained irreversiblemultiorgan damage due to hypoxemia.


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Vascular resistance in the uterine circulationnormally decreases in the first half ofpregnancy due to invasion of maternaluterine vessels by trophoblastic tissue.

Uterine artery Doppler may be most helpful inassessing pregnancies at high risk ofcomplications related to uteroplacentalinsufficiency.

Persistence or development of high-resistance patterns have been linked to avariety of pregnancy complications


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The risk of fetal death before 32 weeks whenassociated with abruption, preeclampsia, orfetal-growth restriction was significantlylinked to high-resistance flow.

They and others suggest continued researchon the role of uterine artery Dopplervelocimetry as a screening tool to detectpregnancies at risk for stillbirth


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Monitoring helps you and your doctor duringyour pregnancy by telling more about thewell-being of the baby. If a test resultsuggests that there may be a problem, this

does not always mean that the baby is introuble. It simply may mean that you needspecial care or more tests. Discuss anyquestions you have about monitoring with

your doctor.


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The most important consideration in decidingwhen to begin antepartum testing is theprognosis for neonatal survival.

The severity of maternal disease is anotherimportant consideration. In general, with the

majority of high-risk pregnancies, mostauthorities recommend that testing begin by 32to 34 weeks.

Pregnancies with severe complications mightrequire testing as early as 26 to 28 weeks. The

frequency for repeating tests has been arbitrarilyset at 7 days, but more frequent testing is oftendone.


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Ante Part Um Fetal Assesment