antepartum assessment
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Transcript of antepartum assessment
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 continuousMay 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