Antepartum Foetal Surveillance,A complete review

1. Antepartum Fetal
Surveillance
Ahmed Shameem

2. Fetal movement count
• It gives a measure of fetal well being.
• Reduction and cessation of movements may precede fetal death by a day or
two.
• A common method is to ask the mother to record the time during which she
has felt 10 kicks. Failure to perceive 10 movements in 12 hour period should
be followed by further biophysical assessment.
• The woman can also be asked to count upto 10 movements in an hour.

3. Nonstress Test (NST)
• NST by cardiotocography is the most commonly used method of assessing
fetal well being.
• It utilizes the physical principle of the Doppler effect in which sound waves
hitting an object are reflected back at an altered frequency.
• In NST the woman is made comfortable either in a left lateral or semi
recumbent position. An external ultrasound transducer for recording fetal
heart rate and tocodynamometer for recording uterine activity are attached to
the mothers abdomen.

4. • The recording is carried out for a period of 20-60 minutes. External
stimulation with palpation can be done if the test remains non reactive.
• The baseline fetal heart rate, beat to beat variability, presence or absence of
accelerations in response to movement and presence and absence of
decelerations is looked for.
• In low risk cases twice weekly NST has been suggested. In high risk cases
associated with IUGR and preeclampsia, daily or even twice daily testing may
be required.

5. Reactive NST
• Presence of 2 or more fetal heart
rate accelerations during a 20 min
period with each acceleration of 15
beats or more per minute and
lasting 15 or more seconds.
Non reactive NST
• It is usually associated with fetal
hypoxia. Other causes are sleep
periods in fetus and GA less than
28 weeks.
• A non reactive NST should be
viewed seriously and actions taken.

6. Vibroacoustic Stimulation Test (VAST)
• An acoustic stimulator is placed on the mothers abdomen and stimulus
applied for 1-2 seconds.
• The basis is that external sound may stimulate fetus provoking fetal heart
rate acceleration in cases thought to be non reactive. This is termed the
startle response.

7. Contraction Stress Test (CST)
• It is also called oxytocin challenge test. This test is based on the fact that the
uteroplacental bloodflow decreases markedly during uterine contractions.
• A normal fetus cam withstand this hypoxic stress without difficulty. But fetus
with chronic or acute problems will not be able to tolerate this decrease in
oxygen supply and this will result in late decelerations.
• If atleast 3 spontaneous contractions of 40 sec or more are present in 10
min, no oxytocin stimulation is needed. If not, contractions are induced with
ocytocin infusion.

8. • A negative test shows no late decelerations or significant variable decelerations.
• A positive test is the presence of late decelerations following 50% or more of the
contractions
• An equivocal test is the presence of intermittent late decelerations or significant
variable decelerations.
• A suspicious test is when inconsistent decelerations are present but not with all
contractions.
• An unsatisfactory test is when there are less than 3 contractions in 10 min.

9. Nipple Stimulation Test
• Nipple stimulation in late pregnancy institutes a neuro hypophyseal reflex
resulting in oxytocin release and uterine contractions.
• The woman is asked to rub one nipple through her clothing for 2 min or
until a contraction begins.

10. Amniotic Fluid Volume
• Assessment of amniotic fluid is an integral part of antepartum fetal
assessment in pregnancies complicated by IUGR and preeclampsia.
• This is based on the fact that decreased uteroplacental perfusion can result in
reduced fetal renal blood flow, decreased fetal urine production and
consequently oligohydramnios.
• Two techniques are used :

11. • Amniotic Fluid Index (AFI)
AFI is calculated by dividingthe uterus into for quadrants and measuring the largest cord free
vertical pocket of liquor in each of the 4 quadrants. The sum of the four measurements is the
AFI in cm.
A range of 5-24 cm is considered normal. Less than 5cm is considered significant
oligohydramnios.
• Single deepest pocket (SDP)
SDP is the depth of a single cord free pocket of amniotic fluid. The normal range is 2-8 cm.
Over 8 cm is considered polyhydramnios and less than 2 cm is considered oligohydramnios.

12. Biophysical Profile
• It is the combined use of 5 variables as a means of assessing fetal wellbeing.
• In fetuses with a normal umblical artery flow on Doppler, the biophysical score is
invariably normal.
• A persistently abnormal BPP is usually associated with absent end diastolic flow.
• Normal variables are given a score of 2 each and abnormal variables a score of 0 .
The highest score possible is 10.
• A score of 8-10 is considered normal ,a score of 6 is considered equivocal and less
than 4 is considered abnormal.

13. Components of BPP
• Nonstress test
Score 2 – atleast 2 accelerations of >15bpm for >15 seconds
Score 0 – 0 or 1 acceleration
• Fetal breathing movements
Score 2- atleast 1 episode of fetal breathing movement lasting >30 minutes
Score 0- <30 seconds of FBM
• Fetal movement
Score 2 – atleast 3 discrete body or limb movements.
Score 0 - <3 discrete movements

14. • Fetal tone
Score 2 – atleast 1 episode of extension of a fetal extremity with return to
flexion or opening or closing of hand
Score 0 – No movements or no extension or flexion
• Amniotic fluid volume
Score 2 – single deepest pocket 2cm or more
Score 0 – Single deepest pocket <2 cm

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