ANTEPARTUM ASSESSMENT

CONTENTS

I. Fetal movementsII. Fetal breathing movementsIII. Contraction stress testIV. Non-stress testV. Biophysical profileVI. Amnionic fluid volumeVII. Umbilical Artery Doppler Velocimetry Current recommendationsSignificance of fetal testing

INTRODUCTION

-In the 1st William obstetric edition 1903: FHR > 160 b/m or < 100 b/m is dangerous -Now the fetus is considered as a 2nd patient

and exposed to serious morbidity and mortality > his mother

-Fetal testing is now extended to the embryonic life:

e.g. Embryonic HR may predict pregnancy outcome

Our goal is to prevent fetal deathFetal death within 7 days of a normal test is very rareIn most tests:

+ve predictive value (true +ve) = 99.8%

--ve predictive value of abnormal tests(true –ve = )10 – 40%

FETAL MOVEMENTS

-FMs starts at 7th week -At 8th week FMs are never

absent > 13 minutes -At 20 – 30 weeks organization

of FMs ( rest - activity cycles) -In the 3rd trimester until 36 weeks

maturation of FMs > -36 weeks behavioral states

BEHAVIORAL STATES

FHR FMs1F quite sleep vvvvvv no2F active sleep VVVVV I3F VVVVV no4F awake state VVVVV IIIIII

+ FHR accelerationsThe presence of F3 is debateContinuous eye movements are present in: 2F, 3F, 4F

At 38 weeks 75% of the time 1F&2FStudy:Urinary bladder ↑ in 1F and ↓ in 2FSleep – awake cycles :

Sleep 20 - 75 minutes Mean = 23 minutes

Maternal perception of FMs is described as: weak - strong - rolling

FMs is α to AFV:As GA ↑ > 20 weeks

weak FMs ↓ vigorous FMs ↑

>32 weeks strong FMs ↓ due to: ↓ AFV ↓ space

Normal FMs : = 4 – 10 FMs / 12 hours

In 1973 ↓ FM precede fetal deathMethods of measuring FMs:

Tocodynamometer U/S Maternal perception

Study :Maternal perception = 80% of FMs by U/SStudy:

> -36 weeks, maternal perception = 16% -Longer FMs > 20 seconds are better felt

Optimal number and duration of FMs: Not defined

Study: Normal FMs = 10 FMs/2 hours

Study : FM/1 hour is good if ≥ previous count

Patient complaint of ↓ FMs in the 3rd T:

Not uncommon = 7% same pregnancy outcome Evaluate & reassure

NST is indicated if: Abnormal fetal growth by U/S Abnormal Doppler

Study: Mean duration to record 10 FMs

= 2.7 hours of counting/dayStudy:

Asking mothers about FMs each visit = counting FMs

II - BREATHING MOVEMENTS

In 1972 inward and outward flows of tracheal fluid in sheep = BMsBMs differ from FMs:

Paradoxical = inspiration collapse expiration distend Not continuous

May be coughing to expel AF debris Essential for fetal development

Types of BMs: Gasps/sighs = 1 - 4/minute Irregular bursts = up to 240c/mAs GA ↑ BMs rate ↓ & volume ↑

At 33 – 36 weeks = lung maturation30 - 40 weeks diurnal variation:

↑ after meals ↓ at night

If BMs are not seen extend U/S evaluation for up to 2 hours before diagnosis of absent BMsFactors affecting BMs:

Hypoxia Sound Hypoglycemia Cigarette

Labor FHR Impending PTL GA

Amniocentesis

BMs as a marker of fetal wellbeing:Unfulfilled because multiple factors itaffect it, but it is included in BPP withOther indices

IV - CONTRACTION STRESS TEST

Basis:Uterine contractions

↑ amnionic fluid P collapse of uterine vessels

isolation of intervillous space transient ↓ O2 exchange

If uteroplacental pathology is present late decelerations

CST is present since 1972Late decelerations:Start at/or beyond the acme of uterine contractionDisadvantages:Require 1 ½ hours

Method:Oxytocin 0.5 mIU/minute by infusion pumpdoubled /20 minutes 3 contractions in

10 minutes duration of each ≥ 40 secondsNipple stimulation:

1 nipple is rubbed through her clothes for 2 minutes or until contractions start, restart

After 5 minutes 3 contractions in 10 minAdvantages: ↓ time and costMay hyperstimulation with mild FD

CRITERIA FOR INTERPRETATION OF CST

Negative: No LD or significant VD Positive: LD + 50% of contractions

even if contractions are < 10/m

Equivocal-suspicious : Intermittent LD Significant VD

Equivocal-hyperactive : LD + > 3 contractions/10m Contraction > 90 seconds

Unsatisfactory : < 3 contractions /10m Uninterruptable tracing

VI – NONSTRESS TEST

1975Basis:FMs FHR accelerations = good signEquipments:

Doppler Maternal perception of FMs

Differ from CST and much easierUsed to discriminate false +ve CSTUsed in BPP

Physiology:Beat to beat variability > 5 b/m + FHR accelerations = good autonomic functionMost common causes of no accelerations:

Fetal sleep Drugs

As GA ↑ ↑ FMs + ↑ FHR accelerations25 – 28 weeks accelerations are

70% 15 b/m for 15 seconds90% 10 b/m for 10 seconds

<32 weeks use 10 b/m for 10 seconds

Normal NST:Vary in number, amplitude & durationof acceleration

=≥2 accelerations that peak at ≥ 15 b/mfor ≥ 15 seconds in 20 minutes ± FM

1 acceleration is enough by someIf no accelerations extend examination to 40-75-80-120 minutes before diagnosis of nonreactive NST

No accelerations = not bad fetusFalse +ve NST ≥ 90%Disadvantages of NST:

↑cost Irreducibility

Computerized analysis: ↓ cost Reliable objective

Abnormal NST: -Silent oscillatory pattern =

ominous = beat - to - beat variability < 5

b/m + no accelerations

-Terminal cardiogram: Both + LD

= uteroplacental insufficiency

Abnormal NST is associated with:FGR 75%Oligohydramnios 80%Acidosis 40%Meconium 30%Placental infarction 93%Study:Nonreactive NST for ≥ 90 min is associated with ↑ perinatal pathology in 93%

Interval between tests:1/week

2/week, 1/day, > 1/day in: Postterm Type 1 DM FGR PIH

Decelerations:Normally present in ½ to 2/3 of fetuses

Variable decelerations : Not ominous if nonrepetitive and brief

<30 secondsRepetitive VD ≥ 3 /20 minutes even if mild are associated with ↑ CS for FDDecelerations ≥ 1 min bad prognosis

Study: -Addition of NST to AFV 75% CS for

FD in cases of ↑ VD + ↓ AFV -FD in labor + normal AFV is increased

in patients with VDFalse - normal NSTs:

= fetal death within 7 days of a normal NST

Mean interval between testing and death: = 4 days Range: = 1 - 7 daysMost common indication of NST:

= posttermMost common autopsy findings:

Meconium Abnormal umbilical cord

=Acute asphyxial insult =NST is inadequate to preclude such an acute asphyxial events

Other causes: Fetomaternal Hg Infection Abruptoplacenta Congenital anomalies Abnormal cord insertion

Acoustic Stimulation Tests:Artificial larynx acoustic stimulationto ↑ accelerationMethod:

External sound for 1 – 2 secondsRepeat 1 – 3 times for up to 3 secondsStill under evaluation

VII – BIOPHYSICAL PROFILE

Manning & colleagues 19805 variables to ↓ false +ve

↓false –ve resultsEquipments:

Doppler Real time U/S

Duration of testing : 1/2 – 1 hour

2 0NST ≥ 2 accelerations < 2

( ≥15 b/m for ≥15 sec in 40 minutes)FBMs ≥ 1 ≥ 30 sec in 30 m < 30 secFMs ≥ 3 in 30m < 3

F Tone ≥ 1-- AFV > 2 cm ≥ 2 cm

( largest single vertical pocket )

Fetal tone = flexion and extension of one limb or opening or closing hand

NST is not required if the 4 variables are normal

AFI if the largest vertical pocket is ≥ 2 cm should be evaluated

BPP = 6 is equivocal and poor predictor of abnormal outcome

BPP = < 6 is progressively more accurate predictor of abnormal outcome

Study:BPP followed by cordocentesis for pH:

-20% of fetuses are FGR -80% of fetuses have alloimmune

hemolytic anemiaBPP = 0 is associated with acidemiaBPP = 8 - 10 is associated with

normal pH

Study:BPP+cordiocentasis in DMno benefitStudy:

BPP+cordiocentasis in GRno benefitThe morbidity and mortality in GR depend on GA & wt not BPP results Modified BPP( abbreviated BPP 1989):

=vibroacoustic NST + AFV X 2/weekDuration of testing = 10 minutes

If AFV is < 5 do complete BPP or CSTCST ↑CS for false abnormal resultsAcceptable by ACOGFalse –ve rate = 0.8 : 1000False +ve rate = 1.5 : 1000Study:

Excellent method with no unexpected FD

MODIFIED BPP MANAGEMENT

BPP = 10: Repeat 1/w

2/w in DM & posttermBPP = 8 -10 + normal AFV :

RepeatBPP = 8 -10 + ↓ AFV :

Chronic fetal asphyxia suspected Deliver

BPP = 6: Possible fetal asphyxia

If > 36 weeks + normal AFV + favorable cervix deliver

If < 36 weeks + normal AFV repeat:

if ≥ 6 deliver if > 6 repeat

If + ↓ AFV deliver

BPP = 4: Probable fetal asphyxia

repeat same day if ≥ 6 deliver

BPP = 0 - 2: Almost certain fetal asphyxia

deliver

VIII – AMNIONIC FLUID VOLUME

Basis:Uteroplacental insufficiency

↓ fetal renal blood flow ↓ urine production

↓ AFVMethods:

AVI Largest vertical pocket 2 x 2 cm pocket

Study: AFI < 5 cm

↑CS for FD ↑low 5 minutes Apgar score

↑perinatal morbidity & mortalityStudy:

20% of fetuses have AFI < 5 cm AFI = poor diagnostic testStudy:Same results in severe preeclampsia

Study:Nonintervention to permit spontaneous

VD in fetuses with AFI < 5 same pregnancy outcome as

induction of labor

IX – UMBILICAL ARTERYDOPPLER VELOCIMETRY

Basis:To assess blood flow by characterizingdownstream impedanceUterine artery S/D ratio:Most commonly useded, abnormal if :

- ↑95th percentile for GA - Diastolic flow is :

Absent (perinatal mortality = 10%)Reversed (perinatal mortality = 33%)

Both absent and reversed diastolic flow are associated with IUGRStudy:NST = DopplerStudy:No benefit other than suggesting GRStudy:No benefit in other diseases as: PIH ,DM, lupus anticoagulant, postterm

Middle cerebral artery S/D ratio:May reflect fetal compromise

Based on brain sparing theory : =uteroplacental insufficiency

↑ blood flow + ↓ impedanceStudy:No significant differenceStill under evaluation

CURRENT RECOMMENDATIONS

No agreement for the best testAll tests have different end points that are considered according to the clinical situationWhen to start?

Most important considerations in decidingwhen to start:

Prognosis of neonatal survival Severity of maternal disease

In high risk patients at 32 – 34 weeks In more severe cases at 26 – 28 weeks

Frequency of testing: ≥ 1/weekIn parkland hospital:All high risk patients are admittedNST 2 – 3/week for admitted cases If FHR accelerations + Deceleration No need for delivery If ↓ FMs or ↓ AFV in 3rd T Admission in labor suit

According to results of NST the patient is:

Discharged Transformed to high risk ward Delivered

Fetal deaths in high risk patients are lowMost fetal deaths are in low risk patients due to unpreventable events as:

Placental abruptions Cord accidents

SIGNIFICANCE OF TESTING

Does it make any difference?Fetal surveillance in 1970s = < 1%

in 1980s = 15%Fetal death rate ↓ in high risk testedpatients # untested patientsStudy:NSTs/CSTs are not recommended because of ↑ cost

Study:No benefit of testing forms of care likely to be ineffective or harmfulCan we identify fetal asphyxia early enough to prevent brain damage?Study:

Abnormal NST is associated with ↓cognition # Doppler = by the time fetal compromise is diagnosed ,

brain damage is already sustained

Study:CP in high risk patients managed by BPP = 1.3 : 1000 live birth

# 4.7 : 1000 in controlsIn a prior report:CP is associated with ↓ BPP scores

=identification is too late

SUMMERY

In the last 2 decades: -Methods are continuously evolving

= dissatisfaction -Wide range of normal variables:

How many accelerations–FMs–FBMs duration and frequency of testing

-Abnormal results are seldom reliable = forecast fetal wellness rather

than illness