Antenatal Surveillance
Ahmet Baschat, MD
Professor
Head, Section of Fetal Therapy
Dep. of Ob/Gyn, Reprod. Sciences
University of Maryland School of Medicine
Antenatal surveillance
• AIM: to prevent compromise & stillbirth
• REQUIREMENTS
–
–
–
–
–
Know limitations of surveillance tests
Recognize specific maternal risk factors
Understand progression of maternal disease
Understand progression of fetal disease
Physical evaluation of the fetus
• PRINIPAL DECISIONS:
– Is delivery indicated ?
– Are steroids indicated ?
– When should the patient be seen again ?
Two important principles
• The need for intervention is based on
the balance of fetal risks versus
neonatal risks
• The monitoring interval has to be
based on the speed of clinical
progression
Pathways of deterioration
adaptation
Not
Fetal
condition
every condition produces
the same clinical
findings
with
INTERVENTION
fetal compromise…
acidemia
hypoxemia
» alterations fetal heart rate pattern
» declining amniotic fluid volume
compromise
» decrease in dynamic variables
» alterations in regional blood flow
Stillbirth
Surveillance tests
• Maternal history and risk factors
• Fetal physical examination
• Anatomy
• Size
• Proportion
• Growth
• Amniotic fluid volume
• Biophysical variables
• Heart rate parameters
• Cardiovascular parameters
Maternal risk factors
•
•
•
Current pregnancy
–
specific referral
–
Hypertension
–
Pre-eclampsia
–
Gestational Diabetes
Prior pregnancy
–
Pre-eclampsia
–
Stillbirth / Losses
–
Abruption
Medical Illness
–
Hypertension
–
Diabetes
–
Lupus
–
Thrombophilia
•
Recognition of maternal risk
factors is essential because it
determines which tests should
be performed and at which
frequency.
•
A thorough history and
physical examination should
form part of the initial
assessment of the patient.
•
Additional laboratory studies
may be indicated to clarify
diagnoses and prognoses.
Fetal risk factors
•
Chromosomal abnormalities, fetal syndromes and viral infections mimic
many potentially treatable fetal conditions.
•
Detailed anatomic survey is therefore essential
– Features of aneuploidy
• Multiple malformations
• Multiple markers
• Abnormal growth
– Features of Syndromes
• Recognized combinations of physical abnormalities
– Viral infection
• Echogenicities in organs
• Fluid accumulation in body cavities
• Abnormal growth
•
These differential diagnoses must be considered at each visit.
Fetal size
• BPD
• HC
• TCD
•
Fetal size is measured by
– Head size
• Biparietal diameter (BPD)
• Head circumference (HC)
• Cerebellar diameter (TCD)
– Body size
• Abdominal circumference (AC)
• AC
– Skeletal size
• Femur length (FL)
• Humerus length (HL)
• FL
• HL
• SEFW
– Estimated fetal weight (EFW)
• Composite varieble
•
Assessment of size requires
reference ranges and knowledge
of gestational age.
Fetal proportion
Percentile
•
Measurements of fetal symmetry:
– Head to abdomen ratios
• (HC/AC)
Percentile
• (TCD/AC)
– Head to Femur ratio (BPD/FL)
– Femur to abdomen ratio (FL/AC)
25
5
•
20
Gestational age
40
– Early growth delay
– Skeletal dysplasia
25
5
Percentile
20
Gestational age
Symetrical small
Asymmetrical
– small abdomen
25
5
20
Gestational age
40
Asymmetrically abnormal size:
Asymmetrical
– short bones
– Trisomy
40
– Syndromes
•
Symmetrically abnormal size
– Severe growth delay
– Aneuploidy
– Viral infection
Fetal growth
Percentile
• Growth is dynamic: single and
serial measurements at >14
day intervals are needed.
AC
= abnormal
AC
AC
AC
AC
AC
AC
25
AC
5
20
AC
– Continued growth along
reference ranges is most
likely normal.
= normal
• Abnormal head growth can
indicate aneuploidy or viral
infection
AC
• Abdominal circumference:
single best measure of fetal
nutrient status.
AC
AC
Gestational age
– measurements that fall off
the curve are likely abnormal.
40
• Skeletal growth abnormality:
important marker for skeletal
dysplasia.
Amniotic fluid volume
After 14 wks a measure of
- fetal urine production
- placental fluid exchange
•
Amniotic fluid index
– Sum of 4 quadrant vertical pockets
– Allows trend-analysis
•
Subjectively reduced fluid
– Maximum pocket < 3 cm
– No fetal bladder filling
– Empty fetal stomach
– Restricted fetal movement
– Flexed fetal position
– Uterine molding around fetus
– Deceleration with movement
– Deceleration with transducer
pressure
– increased uterine contractility
•
Single vertical pocket < 2cm
Amniotic fluid volume
• Fluid volume is determined by the relative rate of
production (urination) and removal (fetal intake).
• If conditions co-exist dynamics may appear normal
(i.e. placental insufficiency and maternal diabetes.
• ↑
fluid – polyhydramnios
• ↓
fluid – oligohydramnios
– Maternal diabetes
– Rupture of membranes
– Tracho-esophageal fistula
– Placental insufficiency
– Choanal atresia
– Viral infection
– Aneuploidy
– Aneuploidy
– Viral infection
– Urinary obstruction
– Tachycardia
– Twin-twin transfusion
– Twin-twin transfusion
Doppler ultrasound
• This standardized approach to
the Doppler examination of
every vessel is essential in
order to achieve reproducible
and reliable results:
21
34
– Zoom to the area of interest
– Apply color Doppler
• Narrow color box
5
• Adjust velocity scale
– Apply pulsed wave gate
• Adjust gate to cover vessel
• Adjust velocity scale
• Adjust filter
– 3-5 uniform waveforms
– No fetal activity
Doppler ultrasound
Velocity
systolic peak
velocity
end-diastolic
peak velocity
systolic peak
velocity
Pulsatility index
S
(S- D)
TAMX
TAMX
S
diastolic peak
velocity
Continuous trace of the
waveform from start to the
beginning of the next
•
In venous vessels automatic
tracing software should not be
used because the triphasic
waveform is not appropriately
analyzed
D
Time
Pulsatility index
(S- a)
TAMX
D
TAMX
atrial systolic
peak velocity
•
a
•
The Pulsatility index is
recommended for arterial
vessels
•
The Pulsatility index for
veins is recommended for
venous vessels
•
Reference ranges should
be used to interpret the
Doppler values
Arterial Doppler
S
•
D
Input pressure
Peripheral resistance
Relationship of systole and
diastolic velocity and
waveform characteristics
depend on
– Input pressure
– Vascular resistance
•
Vessel tone
Vascular histology
Autoregulation
Failed placentation
MCA
Umbilical arteries
Renal
Uterine arteries
Hepatic
Adrenal
Coronaries
Splenic
Vasoconstriction
DA after
Indomethacin
Vascular resistance may be
altered due to
– Changes in vessel tone
– Structural vascular change
Venous Doppler
•
S
D
Venous Doppler gives
information about forward
cardiac function
– Compliance
– Relaxation
– Contractility
Compliance
A
– Afterload
•
Contractility
Afterload
All vessels have the same
waveform
– Systolic peak
– Diastolic peak
– Atrial systole
•
Clinically most studied
– Ductus venosus
60 - 70%
Placenta
– Inferior vena cava
– Umbilical vein
The placenta
Maternal compartment
A two compartment nutrient,
fluid and gas exchange organ
•
Maternal compartment
– Uterine artery Doppler.
11 weeks
•
24 weeks
500-600
ml/min.
40 weeks
12 m2
24 weeks
11 weeks
•
– Umbilical artery Doppler.
•
40 weeks
Maturation of the vasculature
is observed in both
compartments,
– Loss of uterine artery notch
– Appearance of umbilical
diastolic velocity
250 ml/Kg/min.
– Successive decline in
Pulsatility index in both
vessels
•
Fetal compartment
Fetal compartment
Gestational age is important
for assessing waveforms
The placenta
Uterine artery
Umbilical artery
•
Abnormal trophoblast invasion:
– High uterine artery PI
– Persistent uterine artery notch
•
Abnormal villous vascular tree
– Umbilical artery Doppler.
•
Fetal compartment
– 30% abnormal villous
vasculature – high umbilical
artery PI.
– 50% abnormal villous
vasculature – absent umbilical
artery end-diastolic velocity
– 70% abnormal villous
vasculature – reversed umbilical
artery end-diastolic velocity
•
Risk for hypoxemia / acidemia
proportional to decrease in
umbilical end-diastolic flow
Middle cerebral artery
•
Branch of the circle of Willis
– Use parietal bone window
– Parallel to wings of sphenoid
– Proximal part recommended
– Insonate at 0 degrees
•
Two parameters are of
importance in this vessel
•
Decreased pulsatility index in
– Fetal hypoxemia
– Fetal hypertension
– Both are indistinguishable by
the waveform.
•
Increased peak systolic
velocity (0 degree insonation) in
– Fetal anemia
– Increased paCO2
Ductus venosus
•
Is the primary shunt
regulating nutrient flow to
the liver and heart
•
Can be imaged in a saggital
or abdominal transverse view.
•
From the first trimester on
the a-wave should be
antegrade
•
Pulsatility index for veins
significantly decreases with
advancing gestation.
Umbilical vein
•
Examine in the straight abdominal
portion or cord
•
90% of fetuses have constant
flow from 12 weeks on.
•
Pulsations can be
– Monophasic
– Biphasic
– Triphasic
•
Monophasic pulsations are
relevant if central veins are
abnormal
•
Multiphasic pulsations indicate
abnormally high venous pressure
•
Clinical applications:
– Fetal growth restriction
– Twin-twin transfusion
– Hydrops
Abnormal veins
•
The following are abnormal
– Decreased a-wave
– Decreased D-wave
– Decreased v-trough
Constant
•
These abnormalities produce
an increase in the Pulsatility
index for veins
•
Absent or reversed flow
during the a-wave gives a
simple visual assessment of
abnormal ductus venosus flow
Umbilical vein
Fetal behavior
1st trimester
2nd trimester
Behavioral states
3rd trimester
Stable constellation of activity
Cyclicity
Rest activity cycles
Vibroacoustic
Coupling
Glucose & breathing
Movement & FHR
•
Breathing
movement
Activity
Fetal behavior develops
sequentially:
– Isolated activity
– Coupling of behavior
Gross body
movement
– Rest activity cycles
– Behavioral states
•
Movement frequency is
determined by gestational
age and behavioral state
Fetal tone & movement
• Fetal tone can be assessed by examining flexionextension of the extremities and/or the trunk.
• Absence can be explained by
– Fetal hypoxemia
– Fetal acidemia
– Fetal rest
– Neuromuscular block
– CNS abnormality
• Best interpreted in the context of a full biophysical
profile score
Fetal breathing
• Chest movement, diaphragm movement and hiccups count
• Absence can be explained by
– Fasting state
– Fetal hypoxemia
– Fetal acidemia
– Fetal rest
– Neuromuscular block
– CNS abnormality
• Absence of fetal breathing should prompt re-evaluation
after maternal food intake.
Fetal heart rate
cerebral cortex
VMC
RAS • A record of autonomic regulation
of intrinsic cardiac activity and
its modulation by regulatory
centers.
ANS
– Vasomotor center (VMC)
– Reticular activating system (RAS)
– Autonomic nervous system (ANS)
CVS
Heart
BP = CO
x
•
Analyzed visually by
– Baseline heart rate
– Reactivity
peripheral resistance
– Variability
– Periodic changes
stroke volume
x
HR
•
Computerized analysis
– Short term variation (ms)
Fetal heart rate
• Reactivity virtually excludes hypoxemia
• Causes of non-reactivity
– Gestational age
– Behavioral state
– Hypoxemia / Acidemia
– Medications
• Variable decelerations
– Cord compression
• Late decelerations
– >8 torr drop in paO2
– Hypoxemia
• Short term variation <3.5 ms
– Hypoxemia
– Abnormal brain development
Biophysical profile score
For each component presence = 2 points,
absence = 0 points
Tone
Movement
Breathing
Amniotic fluid
Heart rate
at least one episode of active
limb, trunk or hand extension
with return to flexion
•
– Amniotic fluid index
– Reactive FHR
•
– Equivocal (PNM=7-10/1000)
• 8 with oligohydramnios
at least one episode of at least
30 seconds duration (includes
hiccups)
at least 2 acceleration of
- 10 beat x 10 sec (24-28 weeks)
- 15 beat x 15 sec (28-34 weeks)
- 20 beats x 20 sec (>34 weeks)
Manning et al., Am J Obstet Gynecol 1982
Composite score of 5 variables
– Normal = 10, 8 (PNM=1/1000)
at least 3 discrete body/limb
movements (active continuous
considered as single movement)
at least one single vertical
pocket >2 cm
Modified BPS
• 6
– Abnormal (PNM=12-300/1000)
• 6 with oligohydramnios
• 4,2,0
•
Score of 4 – immediate retesting
for 30 min
•
Persistent score of 4, or less –
immediate delivery
0
FHR
parameter
s
LTV <30
reakti
v
STV <3.5
biophysical
parameters
Breathing
Doppler
Parameter
Tone &
Movement
Δ pH
-2
-4
-6
pH <
7.20
-8
pH < 7.10
abnormal cCTG und Ductus
venosus
comparable pH
-10
NST
cCTG*
AFV
biophysical parameter =
closer relationship with pH
FBM
FGM
Tone
AEDV TAO DAO
MCA
CPR
Akalin-Sel et al., Arduini et al., Bilardo et al., Guzman et al,, Hecher et al,, Nicolaides et al., Ribbert et al., Rizzo et al., Soothill et al., Visser et
al., Weiner et al.
DV
Summary
Tests provide specific information
Fetal anatomy – differential diagnosis
Fetal growth – placental performance
Amniotic fluid – volume status / placental transfer
Uterine Doppler – trophoblast invasion
Umbilical Doppler – vascular exchange area
MCA Doppler – pCO2, Hgb, Oxygen, Hypertension
Venous Doppler – rhythm, forward cardiac function
Dynamic variables – Maturation, Behavioral state, pO2
FHR variables – CNS, PNS, pO2
Specific conditions require specific tests…
Pathways of deterioration
adaptation
Not
Fetal
condition
every condition produces
the same clinical
findings
with
INTERVENTION
fetal compromise…
acidemia
hypoxemia
» alterations fetal heart rate pattern
» declining amniotic fluid volume
compromise
» decrease in dynamic variables
» alterations in regional blood flow
Stillbirth
Integrated fetal testing
• Every surveillance test has advantages and
disadvantages
• Integrated fetal testing combines different
tests as needed
– Distinguishing false positives from true positives
– Detect different avenues of fetal deterioration
• Examples of integrated testing
– Biophysical profile score
– Fetal Apgar Score
– Integrated fetal testing management
Fetal growth restriction
FGR before 34 weeks
*
*
*
CIRCULATORY
COMPROMISE
Ductus venosus
CIRCULATORY
DECOMPENSATION
PLACENTA – BASED
Umbilical artery
GROWTH DELAY
BPS
Middle cerebral artery
CIRCULATORY
COMPENSATION
Delayed maturation of FHR control
DEVELOPMENTAL
DELAY
Increased baseline
variation decrease / loss
Decreased variation / variability
Decreased reactivity
ABNORMAL
DECLINING
declining amniotic fluid volume
BPS
ACTIVITY
declining global activity
Loss of
breathing
Loss of movement
Delayed behavioral maturation
Loss of tone
Δ pH
0
-2
*
HYPOXEMIA
ACIDEMIA
STILLBIRTH
-4
Baschat 2008
FGR after 34 weeks
Ductus venosus
PLACENTA – BASED
GROWTH DELAY
Umbilical artery
Middle cerebral artery
Nonreactive heart rate
declining amniotic fluid volume
Loss of breathing
Δ pH
0
-2
-4
?
STILLBIRTH
Baschat 2008
Approach to the fetus with small biometry
Anatomy
abnormal
Likely diagnosis
Aneuploidy
Syndrome
normal
Amniotic fluid
increased
Viral infection
normal or decreased
elevated index
Absent / reversed
end-diastolic velocity
Umbilical artery Doppler
normal
Middle cerebral artery Doppler
decreased index
IUGR due to
placental
insufficiency
normal
Cerebroplacental ratio
decreased ratio
normal
normal repeat examination at 14 days
Constitutionally
small fetus
The principal decisions
The monitoring interval
Early stages require less frequent monitoring
Disease acceleration = ↑ monitoring frequency
New onset brain sparing
Oligohydramnios
UA – AEDV / REDV
Abnormal DV Doppler
Which thresholds to base delivery on ?
Early gestation = high threshold
Late gestation = low threshold
Severe
↑
↓
UA PI
Cerebroplacental Doppler ratio
UA A-REDV
Brain sparing
Abnormal DV index
DV RAV – UV pulsations
Progressive
↑
↓
UA PI
Cerebroplacental Doppler ratio
Brain sparing
UA A-REDV
Abnormal DV index
DV RAV – UV pulsations
27 day latency
30 weeks delivery
38 day latency / 33.4 weeks delivery
↓
↑
Mild
CPR
UA PI
46 day latency / 35.3 weeks delivery
27
29
31
33
35
37
39
Gestational weeks
Turan OM et al., Ultrasound Obstet Gynecol 2008
After diagnosis of FGR:
-Weekly UA Doppler
-Severe deteriorates within 2 weeks
-Progressive deteriorates over next 2 weeks
- If no change over 4 weeks – probably mild
Turan OM et al., Ultrasound Obstet Gynecol 2008
100
90
1%/day in utero
N=642
Overall mortality = 130 (21%)
Intact survival = 352 (54%)
80
2% / day in utero
70
60
Percent
50
Neonatal survival
40
Intact survival
30
20
10
0
24
25
26
27
28
29
30
31
32
Baschat et al., Obstet Gynecol 2007
Prospective Stillbirth rate
2.5
prospective stillbirth rate
Risk / 1000 ongoing pregnancies
prospective perinatal mortality rate
2
Favor
delivery for
singletons
1.5
1
0.5
0
24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
Kahn et al., Obstet Gynecol, 2002
• If Fetal growth
restriction is
observed at 38
weeks the
statistical benefit
of delivery
outweighs the risk
of continuing
pregnancy
Divon et al., 1989, AJOG
•
•
•
•
Clinical trial
IUGR fetuses with A/REDF
Daily BPS
Delivery for
–
–
–
–
BPS of 4 or less
Oligohydramnios
maternal status
documented lung maturity
• No stillbirths, no acidemia at birth
Cosmi et al., 2005, Obstet.
Gynecol
• 145 idiopathic IUGR; delivery for BPS or CTG
• Two groups of fetuses
–
–
–
complete deterioration of all Doppler parameters
Abnormal BPS / CTG with maintained Dopplers
No differences in perinatal outcome
• Predictors of outcome
– UA REDV
– DV REDV
– Birthweight
• Even with DV A/REDV up to 8 days normal BPP !
Combined tests – hypothetical modeling
100
Percent ongoing pregnancies
80
modified BPP & AREDV
DV RAV or UV Pulsations
and
absent movement or fluid
11/17 stillbirths prevented
12/ 24 Acidemia prevented
28.0 weeks delivery GA
18/29 stillbirths prevented
17/30 Acidemia prevented
29.3 weeks delivery GA
15% increase in survival
60
Abnormal BPP alone
19/29 stillbirths prevented
18/30 Acidemia prevented
28.5 weeks delivery GA
8% increase in survival
40
20
0
24
25
26
27
28
Gestational week
29
30
31
32
Baschat et al., AJOG 2007
Intervention triggers
TRUFFLE
individualize
STV < 3.5 msec
STV < 4 msec
DV - RAV
DV PI > 3SD
UA - REDV
UA-AEDV
Biophysical profile score < 6
Integrated fetal testing score < 8
Greatest survival benefit / day in
utero
Periviability
24
26
Steroids beneficial
29
32
Not well
delineated
34
Baschat 2008
Maternal Diabetes
140
mg/dl
130
Increased insulin
resistance
GLUCOSE
120
110
Higher postprandial
glucose
100
90
80
Lower fasting glucose
70
60
250
IU / ml
200
INSULIN
Non-pregnant
Pregnant
Potential risk to develop
diabetes in pregnancy
150
100
50
0
Risks of worsening
glycemic control in
existing diabetes
Diagnosis
Current pregnancy
Duration
Fasting
sugar
<105 mg%
>105 mg%
1’ sugar
<140 mg%
>140 mg%
Therapy
Diet
> Age
20
Age
10-19
Age
<10
<10
years
10-19
years
>20
years
Insulin
Insulin
Vascular
risks
Whites Class A 1
Benign
NephroRetinopathy pathy
A 2
B
C
D
Cardiac
R
H
F
Macrosomia
Pregnancy
risks
Proliferative
Retinopathy
IUGR
Fetal death
Anomalies
PIH / PET
Maternal Mortality
Surveillance in diabetes
• Signs of glycemiamediated risks
• Signs of vascularmediated risks
– Macrosomia
– IUGR
– Polyhydramnios
– Abnormal uterine
artery Dopplers
– Myocardial thickening
Monitor fluid & FHR
Monitor like IUGR
Once / twice weekly
Once / twice weekly
Empiric monitoring based on GA
Start monitoring in the presence of above signs
Anti Ro/La antibodies
A
E
MV
AAO
•
Anti Ro/La (SSA/SSB)
autoantibodies of the IgG
class can pass the placenta
from 12 weeks on.
•
In the fetal circulation they
can lead to irreversible
destruction of the
myocardium and conduction
tissue.
•
Doppler measurement of the
PR-interval allows detection
of a first degree heart block
(>130 ms).
•
Therapeutic Dexamthasone
can prevent progression to
complete heart block
Fetal SVT
Reappearance of normal
venous pattern
Cardioversion
•
The risk of hydrops is
related to the rise in central
venous pressure that occurs
when triphasic venous flow is
lost.
•
The earliest sign of therapy
success is the reappearance
of triphasic venous flow
•
This is followed by
cardioversion to normal heart
rate…
•
And finally resolution of post
SVT cardiomyopathy
Resolution of cardiomyopathy
Monochorionic pregnancies
Surveillance in monochorionic
twins
• Surveillance should integrate the following information:
– Growth dynamics
– Fetal volume status
• Amniotic fluid index
• Bladder filling
– Vascular parameters
• Umbilical artery Doppler
• Middle cerebral artery Doppler
• Venous Doppler
– Biophysical parameters (esp. in growth restriction)
Anemia - pathophysiology
Alterations in blood flow dynamics
Detectable elevation of blood flow
velocity
Doppler correlates with fetal hemoglobin
value
Middle cerebral artery
Fetal anemia
Mari et al., Obstet Gynecol 2002
» Prediction of fetal anemia
» sensitivity 100 % (86-100), false +ve rate 12%
» responds to correction of anemia
» retains sensitivity to time repeat transfusions
» Correlation improves with degree of anemia
» Utility in other conditions associated with anemia
» Parvovirus infection
» TTTS
» Non-immune hydrops
Mari et al., NEJM 2000; Detti et al., AJOG 2001 , Stefos et al., AJOG 2002, Cosmi et al., AJOG 2002;
Ohkuchi et al., UOG 2002, Hernandez-Andrade UOG 2004
Fetal hydrops
Hydrops pathophysiology
Abnormal preload
Alterations in forward cardiac function
Doppler gives diagnostic / prognostic thresholds
Anemiarelated
issues
Prognosis
MCA PSV
Structural problems
>70 % mortality
Cardiac
disease
Venous Doppler
Doppler in Hydrops
Critical diagnostic tool
Prognostic assessment
Allows for monitoring of potentially
treatable lesions – CCAM, Sacrococcygeal
Teratoma
Post-dates pregnancy
2.5
prospective stillbirth rate
•
Correct routine first
trimester ultrasound dating
almost halves rates of postterm inductions.
•
In properly dated pregnancies
3 % go beyond 42 weeks
•
Risks of stillbirth are related
to placental ageing.
•
No specific sequence of
progression has been
described to direct
surveillance
•
Rapid decline of amniotic
fluid volume is typical
Risk / 1000 ongoing pregnancies
prospective perinatal mortality rate
2
Favor
delivery for
singletons
1.5
1
0.5
– Twice weekly surveillance
0
24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
Kahn et al., Obstet Gynecol, 2002
•
Induction at 41 weeks
decreases stillbirth rate
significantly.
Conclusion
Surveillance should be disease specific
Testing frequency should be based on
disease acceleration
Intervention thresholds should be based
on intrauterine versus neonatal risks