1. Antepartum fetal
surveillance
-jason zachariah
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2. Introduction:
• Majority of the fetal deaths(80%) occur in the antepartum
period.
• The major causes of deaths are: 1) chronic fetal hypoxia(IUGR)
2) maternal complications-diabetes, hypertension, infection
3)fetal congenital malformation 4) unexplained causes
• The primary objective of antenatal fetal assessment is to avoid
fetal death
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3. Monitoring methods
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4. Clinical monitoring:
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5. Special invvestigations:
Early pregnancy
Biochemical Biophysical Cytogenetic
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6. Biochemical:
• Maternal serum AFP
• Triple test
• Acetyl choline esterase test
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7. AFP:
• It is an oncofetal protein produced by yolk sac and fetal liver
• Highest level in fetal serum and amniotic fluid is reached
around 13 weeks and thereafter it decreases
• Maternal serum level reaches a peak around 32 weeks
• Test is done between 15 to 20 wks
MSAFP is elevated in a number of conditions:
 Wrong GA
 Open neural tube defects
 Multiple pregnancy
 IUFD
 Anterior abdominal wall defects
 Renal defects
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8. Triple test:
• Combined test which includes MSAFP,hCG and UE3
• It is used for the detection of Down’s syndrome
Acetyl choline esterase
• Elevated in open neural tube defects
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9. Cytogenetic
• Amniocentesis
• Chorionic vilus sampling
• Cordocentesis
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10. Amniocentesis
This procedure
involves tapping of
the amniotic sac
either for
diagnostic
purposes (to obtain
a sample) or for
therapeutic
purposes, under
ultrasonic
guidance.
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11. Diagnostic indications
• Early months(15-20 wks)Sex linked disorders
Karyotyping
In born errors of metabolism
Neural tube defects
• Later months
Fetal maturity
Degree of fetal hemolysis in Rh sensitised mother
Meconium staining of liquor
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12. Therapeutic indications:
• First half:
Abortion induction by instilling chemicals
Repeated decompression of uterus in acute hydramnios
• Second half
Decompression of uterus in unresponsive c/c hydramnios
Fetal transfusion
aminoinfusion
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13. Chorionic villus sampling
• Prenatal diagnosis of genetic
disorders
• Carried out transcervically
between 10-12 weeks and
transabdominally from 10 wks till
term
• A few villi are collected from the
chorion frondosum under
ultrasonic guidance with the help
of a long maalaeble polyethylene
catheter introduced transcervically
along the extraovular space
• Provides diagnosis in 24 hours
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14. • Complications: fetal loss, oromandibular limb deformities,
vaginal bleeding- higher when compared to amniocentesis
• False positives due to placental mosaics and maternal cell
contamination can occur. In such cases, amniocentesis to
confirm.
• Anti-D should be given to Rh-ve mother following procedure
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15. Cordocentesis
• Percutaneous umbilical blood sampling
• All information obtained from
amniocentesis and CVS can be
obtained. In addition,
Fetal anemia, bleeding disorders,
hemoglobinopathies
Fetal infections-toxoplasmosis, viral
Fetal blood gas and acid base status- in
IUGR
Fetal therapy- in blood transfusion
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16. Biophysical
• Ultrasonographic examination of fetus
CRL-smaller than GA-chr anomalies
Increased nuchal translucency
Absence of nasal bone
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17. Antepartum surveillance-late
pregnancy
• Clinical
• Biochemical-mainlly to assess lung maturity
• biophysical
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18. Biophysical tets
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Fetal movement count
Cardiotocography
Nonstress test
Fetal biophysical profile
Doppler ultrasound
Vibroaccoustic stimulation
Contraction stress test
Amniotic fluid volume
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19. Fetal movement count
Cardif ‘count 10’ formula: the patient is instructed to
report if 1)less than 10 movts occur during 12 hours on 2
consecutive days or 2)no movts percieved even after 12
hrs in a single day
DFMC- three counts each of one hour(morning,noon and
night) are recommended. The total counts multiplied by
4 gives the dfmc
Loss of fetal movts is commonly followed by
disappearance od FHR within next 24 hrs
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20. NST
• Currently most commonly used
• Utilises principle of Doppler ultrect
• An external ultrasound transducer for recording fetal heart
rate and tocodynamometer for recording uterine activity are
attached to maternal abdomen
• This test is based on the hypothesis that the heart rate of a
fetus that is not acidotic due to hypoxia will accelerate in
response to fetal movt
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21. Reactive NST
• Presence of 2 or more fetal heart rate accelerations during a
20 min period, with each acceleration of 15 beats per min
lasting 15 sec or more, usually occurring simultaneously with
fetal movement. Tracing is extended to 40 mins before
commenting non reactive
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22. Non reactive NST
• Usually associated with fetal hypoxia
• Other causes- sleep periods in fetus and GA<28 weeks
• Variable decelerations if non repetitive and brief are not
significant. But repetitive( atleast 3 in 10min) or prolonged
(more than 30 sec) variable decelerations are considered
abnormal
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23. VAST
• An acoustic stimulator is placed on the maternal abdomen
and a stimulus applied for 1-2 sec. the basis is that the
external sound may stimulate the fetus provoking fetal heart
rate acceleration in cases thought to be non reactive. This is
termed startle response
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24. Contraction stress test
• Also termed oxytocin challenge test
• This test is based upon the fact that the utero-placenttal
blood flow decreases markedly during uterine contractions.
• A normal fetus can withstand this hypoxic stress without
dirfficulty
• A fetus with acute or chronic problems will not be able to
withstand this decrease in qxygen supply and this will result in
late decelerations
• If atleast 3 spontaneous contractions lasting atleast 40 sec is
present in 10 mins, oxytocin stimulation is not needed
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25. • If atleast 3 spontaneous contractions lasting atleast 40 sec is
present in 10 mins, oxytocin stimulation is not needed
• If not contractions are induced with oxytocin infusion
• This test gives an indication whether the fetus will withstand
the stress of labour
• Disadvantages-time consuming, invasive and can rarely cause
severe fetal hypoxia
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26. Biophysical profile
• A set of 5 variables, which depends upon the integrity pf the
CNS, used to assess fetal well being
• It can be used to decide on the timing of delivery in high risk
cases such as IUGR
• A persistently low BPP is always associated with absent end
diastolic flow
• Normal variables are given a score of 2 each and abnormal
variables are given zero points
• Indication: Non reactive NST, High risk pregnancy
• Test frequency: weekly after a normal NST, twice weekly after
abnormal NST
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27. Biophysical profile
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28. BPP scoring, interpretation and
management
BPP score
interpretation
management
8-10
No fetal hypoxia
Repeat testing at weekly
interval or more
6
Suspect chronic asphyxia
If>36wks, deliver
If L/S<2.0, repeat test in
4-6 hours
4
Suspect chronic asphyxia
If>/= 36 wks, deliver
<32 wks-repeat testing in
4-6 hrs
0-2
Strongly suspect
asphyxia
Test for 120 mins-if
persistent score of </=4,
deliver regardless of GA
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29. Modified BPP
• Consists of NST and USG determined AFI
• Considered abnormal if NST non reactive or AFI<5cm
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30. Fetal cardiotocography
• A normal tracing after 32 weeks would show a baseline heart
rate of 110-150 bpm with an amplitude of baseline variability
5-25 bpm
• There should be 2 or more accelerations in a 20 min period
• There should be no decelerations or there may be early
deceleration of very short duration
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31. USG
• IUGR can be diagnosed accurately with serial measurement of
BPD, AC, HC, FL and amniotic fluid volume.
• AC is the single best measurement of fetal nutrition status
• HC/AC ratio is elevation(>1) after 34 weeks should raise
suspicion of IUGR
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32. Doppler ultrasound
velocimetry
• Doppler flow velocity wave forms are obtained from arterial
and venous beds in the fetus
• Arterial doppler wave form is helpful to assess downstream
vascular resistance. It is used to measure peak systolic(S),
diastolic(D) and mean (M) volumes
• From these values, S/D ratio, pulsatility index(PI=(S-D)/M), or
resistance index(RI=(S-D)/S)
• I
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33. • In normal pregnancy, the S/D ratio, PI and RI decreases as GA
advances
• Higher values greater than 2 SDs above gestational age mean
indicates reduced diastolic velocities and increased placental
vascular resistance. These features point towrd adverse
pregnancy outcome
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36. • Venous doppler parameter provides information about
cardiac forward function(cardiac compliance, contractility and
afterload).
• Fetuses with abnormal cardiac function show pulsatile flow in
the umbilical vein. Normal UV flow is monophasic
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37. Antenatal doppler changes and the features
suggestive of a compromised fetus:
Vessel
Change
Pathophysiological Clinical
basis
significance
Umbilical
artery(UA)
Reduced or
absent end
diastolic flow
Failure of villous
trophoblast
invasion
Middle cerebrral
artery(MCA)
Increased diastolic Dilatation of
velocity,
cerebral vessels
Decresed S/D or
PI
“brain sparing’
effect in
response to
hypoxemia
Ductus venosus
High doppler
index
Absent or
reversed flow
Increased CVP
Fetal acidemia
Umbilical vein
(UV)
Increased doppler
index,
Pulsatile flow
Increased CVP or
decreased cardiac
compliance
Fetal acidemia
Increased
resistance in
fetoplacental
circulation-IUGR,
preeclampsia
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38. Amniotic fluid volume
• An ntegral part of AFS in pregnancies complicated by IUGR and
pre-eclampia
• Decreased uteroplacental perfusion can result in reduced fetal
renal blood flow, decreased fetal urine production and
consequently oligohydramnios
• Oligohydramnios can be due to pre-eclampsia, IUGR, PROM
and fetal renal agenesis or urinary tract obstruction.
• 2 techniques
AFI
SDP
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39. AFI
• It is calculated by dividing the uterus into 4 quadrants and
measuring the largest vertical pocket of liquor in each of the 4
quadrants.
• The sum of the 4 measurements is AFI in cm
• Range of 5-25 is considered normal
• <5 – significant oligohydramnios
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40. SDP
• It is the depth of a single cord free pocket of amniotic fluid.
The normal range iss 2-8 cm. over 8cm is considered
polyhydramnios. Less than 2cm is considered oligohydramnios
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41. Other tests in late pregnancy
• Tests for fetal lung maturity
• Assessment of severity of Rh isoimmunisation
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42. References
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D.C.Dutta’s textbook of obstetrics- 7th edition
Textbook of obstetrics- Sheila B
Mudaliar and Menon’s textbook of obstetrics
Google- for the images
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