Objectives: Antenatal Fetal Surveillance
Antenatal Testing:
Who, What, When, Where, Why?
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Review evidence to guide surveillance:
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Brian L Shaffer MD
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Assistant Professor
Department of Obstetrics and Gynecology and Medical Genetics
University of California, San Francisco
6/10/10
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Patient selection
Technologies
Techniques
Timing
Location
Effectiveness
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Goals?
Evidence is limited
Who, What, When, Where, Why?
Antenatal Testing: Why?
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Why?
Improve Perinatal Outcomes!
• Prevent Intrauterine Fetal Demise (IUFD)
• Identify at risk fetuses:
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Intrauterine neurologic injury
Timely intervention
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Delivery
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Induction of labor
Cesarean
Balance potential benefits
Inconveniences, Cost, Limitations
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IUFD - background
Far too common!
Worldwide: 3.2 million/year
US: 26,000/year
Incidence - 6.4/1000
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IUFD: Decline in fetal status
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Fetus with growth restriction
Loss of Fetal Heart Rate (FHR) reactivity
Abnormal blood flow in umbilical artery
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20-27 weeks 3.3/1000
>28 weeks 3.2/1000
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Abnormal biophysical parameters
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Blood flow is redirected from kidneys oligohydramnios
Hypoxemia/acidemia
Fetal injury/death
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4.1/1000
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IUFD – Associated conditions
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Maternal medical conditions
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HTN, DM, Renal, Thyroid, Liver
Cholestasis, Connective tissue disorders
Antiphospholipid AB, Thrombophilia, Alloimmunization
Congenital anomaly or malformation
Chromosomal (fetus or placenta)
Fetomaternal hemorrhage
Placental abnormalities (e.g. vasa previa, abruption)
Umbilical cord (e.g. velamentous, prolapse, occulsion)
Multifetal gestation (e.g. TTTS, TRAP)
Abnormal serum markers (e.g. low PAPP-A)
Infection
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Maternal, placental, leading to preterm labor
Followed by MCA, DV
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23% decrease since 1990
Healthy People 2010
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Biophysical or Doppler examination
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“Late” IUFD
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Predictable and sequential changes
Decreased breathing, body movements, tone
Antenatal Testing: What?
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Fetal Movement Counting
Contraction Stress Test (CST)
Biophysical Profile (BPP)
Non Stress Test (NST)
Modified BPP (NST/AFI)
Doppler interrogation
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Umbilical artery (UA)
Ductus venosus (DV)
Middle cerebral artery (MCA)
Uterine artery
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Fetal Movement Counting
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Regular movements ~20 weeks
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10 movements in 12 hours
10 movements in 2 hours, focus on fetus
4 movements in 1 hour, focus on fetus
What is decreased fetal movement?
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Frequency unchanged
Quality change
Kick counts in practice
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Contraction Stress Test (CST)
Contractions decrease O2 delivery
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Hypoxic fetuses have late decelerations
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Elucidates subtle compromise
May aid in predicting tolerance of labor
CST
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IV Oxytocin
Nipple stimulation
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Faster
Hyperstimulation
3 UCs, 40 sec in duration, in 10 minutes
Overall maternal sense
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Evaluation (history review, NST, ultrasound)
CST – Management
Contraction Stress Test (CST)
CST result
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Negative CST
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Reactive–negative
Repeat, 7 days
Nonreactive-negative
Repeat, 24 hours
Evaluation for nonreactivity
Fetus <28 weeks, normal variability,
repeat in 7 days
IUFD, CD for NRFHT, low Apgar scores
Reactive-equivocal
Repeat, 24 hours
30% tolerate labor without FHR changes
Nonreactive-equivocal
Repeat, 12-24 hours
Reactive-positive
Gestational Age >37wks, trial of induction
Preterm: further evaluation
Nonreactive-positive
Term: delivery via cesarean
Preterm: further testing
Rate of stillbirth in 7 days: 4/10,000
Positive CST
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50% poor perinatal outcome
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Limitations
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Follow-up
Contraindicated when unable to tolerate
contractions (e.g. placenta previa)
Timing, Staff, Labor unit
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Biophysical Profile (BPP)
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Non Stress Test (NST) with ultrasound
Acute & chronic fetal compromise
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Oligohydramnios - associated with acidemia
Amniotic Fluid Index (AFI)
Deepest Vertical Pocket (DVP)
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Others parameters – acute
5 Components tallied for score
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NST
Amniotic Fluid Volume
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Amniotic fluid volume – chronic
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Biophysical Profile (BPP)
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Not all measures equal
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Poor sensitivity
• True oligo or polyhydramnios
“Chronic” variable
Breathing
Movements
Tone
BPP Management
Non-Stress Test (NST)
Score
Risk of Asphyxia
Management
Perinatal
Mortality*
10/10
8/10 (AFI nl)
Nearly zero
Follow as clinical course
dictates
<1/1000
8/10 (Oligo)
Chronic asphyxia likely
Normal urinary tract, no ROM,
delivery after steroids
20-30
6/10 (AFI nl)
6/10 (Oligo)
Asphyxia not excluded
Chronic Asphyxia likely
Repeat. If 6/10,
deliver at >37 weeks
If immature repeat within 24h
If less than 6/10 delivery
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>50
4/10
Acute likely, if oligo, risk of
acute and chronic increases
Delivery, continuous FHT
115
>115 if oligo
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2/10
Acute with chronic
asphyxia likely
Delivery, typically via
cesarean
220
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0/10
Nearly certain
Deliver Immediately
550
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Benefits: Less invasive, time consuming
Procedure / Definition
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Semi-Fowler’s with L lateral tilt
Baseline, variability, and accelerations
Reactive NST
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Normal Baseline (110-160 bpm)
Moderate Variability (5-25 bpm)
Accelerations (15 bpm x 15 sec)
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10 x 10 < 32 weeks
* risk of fetal mortality (per 1000) within one week without any fetal intervention
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Non-Stress Test (NST)
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Factors that modulate accelerations
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Sympathetic discharge
Fetal circadian rhythm - sleep
Maternal medication/illicit drug
Decreased FHR reactivity
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Smoking
Fetal non-REM sleep
NST - Interpretation
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Variables
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Non-repetitive, <30 sec, otherwise reactive
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Not infrequent (up to 50%)
No action needed
≥ 3 variables: Increased C/S for FIOL
Deceleration > 60 sec
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Associated with IUFD
Cesarean for non-reassuring FHT
NST - Interpretation
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Non-reactive NST
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≥ 40 minute – fetal compromise?
Consider Gestational Age
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NST Performance
24-28 weeks - 50% healthy
28-32 weeks - 15% of healthy
Back-up test if abnormal
Reactive NST
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“False positive”
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VAS – Safe and Effective
Glucose & manual stimulation
No difference
3.1/1000; (1.9-5/1000)
Nonreactive NST
Help
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Normal FHR, but IUFD within 7 days
“False negative”
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55% - Back-up testing is normal
“True positive”
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20% poor outcome
• IUFD, late decelerations, low Apgar scores
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Comparison of Tests
Modified Biophysical Profile
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False Negative*
False Positive#
NST
19-65
50-90%
Modified BPP
~8
60%
CST
4
35-65%
BPP
~8
40%
NST – short term assessment
Amniotic fluid index (AFI)
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Test
Hypoxemia → renal perfusion → oligohydramnios
False positive: (non-hypoxic at delivery) 60%
False negative: (IUFD after normal test) 0.8/1000
Intervention
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Higher cesarean: 2 fold increase in RR
Iatrogenic PTB in ~1-2%
* risk of fetal mortality (per 10,000) <1 week after a negative test result
# fetal survival >1 week after a positive test result
Doppler Velocimetry
Doppler: Uterine artery
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Uteroplacental blood flow
Fetal physiologic responses
Best evidence
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Adjunct
Primary surveillance
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Early IUGR
Abnormal placentation
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Inadequate trophoblast invasion and spiral artery
remodeling
Increased impedance in uterine artery
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Notching at 22-24 weeks
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Reduced flow to placental unit
Associated with future pre-eclampsia, IUGR, and death
No benefit:
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Low risk population
Primary surveillance
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Doppler: Middle cerebral artery
Doppler: Umbilical artery - IUGR
Associated destruction of villous vasculature
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Increased systolic: diastolic ratio
Absent, or reversed diastolic flow
• Fetal hypoxia, morbidity, & mortality
• Cesarean, NICU admission, neurodev delay
Early onset IUGR due to placental insufficiency
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Decreased antepartum admission, induction
Trend toward ↓ mortality - OR 0.71 (95 % CI, 0.5-1.01)
Doppler: Ductus Venosus
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Compromised fetus
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Decreased blood
flow to periphery
Increased flow to brain
“brain sparing effect”
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Decreased S/D ratio
Poor predictor
of adverse outcomes
Antenatal testing: Who & When?
Indication
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Fetal veins
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Cardiac function
Regulates oxygenated blood in fetus
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Resistant to changes except in severe IUGR
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Earliest sign increased shunting (prior to lag in AC)
• Increased placental resistance RV can’t compensate
LV increases work spares the heart & brain
Late sign excessive shunting followed by reversal of flow
is associated with a ~40% risk of stillbirth
Low risk
GDM A1
DM insulin
Chronic HTN
Pre-eclampsia
Pre-e, Severe
IUGR
Twins
Triplets
Stillbirth
(per 1000)
6.4
6-10
6-35
6-25
9-51
12-29
10-47
12
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Odds Ratio
0.86
1.2-2.2
1.7-7
1.5-2.7
1.2-4
1.8-4.4
7-11.8
1-2.8
2.8-3.7
Gestational
Age (wks)
28-32
32
At Dx
At Dx
At Dx
28-36
28
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Antenatal testing: Who & When?
Indication
Oligohydramnios
Post term 41
Post term 42
h/o IUFD
Decreased FM
SLE
Renal disease
Cholestasis
ART
Stillbirth
(per 1000)
14
1.6
2-3.5
9-20
13
40-150
15-200
12-30
12
Odds Ratio
4.5
1.5
1.8-2.9
1.4-3.2
2.5-5.6
6-20
2.2-30
1.8-4.4
2.6
Gestational
Age (wks)
At Dx
40 ½
40 ½
32
At Dx
32
28-32
At Dx
36
Antenatal testing: Who & When?
Indication
AMA 35-39
AMA ≥ 40
PAPP-A < 1st
>2 Abnl Markers
Obesity BMI > 30
BMI 25-29
Smoking >10 cig/d
Thrombophilia
Thyroid
Antenatal Testing: Benefits and Costs
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Limited data on benefits
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Testing, interpretation
Interventions
Iatrogenic prematurity
Anxiety
Unclear if the costs and risks outweigh the gains
Odds Ratio
1.8-2.2
1.8-3.3
2.2-4.0
4.3-9.2
2.1-2.8
1.9-2.7
1.7-3.0
2.8-5.0
2.2-3.0
Gestational
Age (wks)
36
32
32
32
32
32
32-36
Antenatal Testing: Conclusion
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Kick counts
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Prevent IUFD?
Costs
Stillbirth
(per 1000)
11-14
11-21
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8-18
13-18
12-15
10-15
18-40
12-20
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Use evidence
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Choose wisely who and when
NST/AFI back up CST/BPP
Doppler with IUGR: UA, DV
Limit intervention if possible
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May “capture” those at low risk
Prematurity
Further research
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