antenatal surveillance ahmet baschat, md professor head, section of fetal therapy dep. of ob/gyn,...
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Antenatal Surveillance
Ahmet Baschat, MD
ProfessorHead, Section of Fetal TherapyDep. of Ob/Gyn, Reprod. SciencesUniversity 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
Fetal condition
hypoxemia
Stillbirth
compromise
acidemia
» alterations fetal heart rate pattern
» alterations in regional blood flow
» decrease in dynamic variables
» declining amniotic fluid volume
INTERVENTION
Not every condition produces the same clinical
findings with fetal compromise…
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
• AC
• FL• HL• SEFW
• Fetal size is measured by– Head size
• Biparietal diameter (BPD)
• Head circumference (HC)
• Cerebellar diameter (TCD)
– Body size• Abdominal circumference
(AC)
– Skeletal size• Femur length (FL)
• Humerus length (HL)
– Estimated fetal weight (EFW)• Composite varieble
• Assessment of size requires reference ranges and knowledge of gestational age.
Fetal proportion• Measurements of fetal
symmetry:– Head to abdomen ratios
• (HC/AC)
• (TCD/AC)
– Head to Femur ratio (BPD/FL)
– Femur to abdomen ratio (FL/AC)
• Asymmetrically abnormal size:– Early growth delay
– Skeletal dysplasia
– Trisomy
– Syndromes
• Symmetrically abnormal size– Severe growth delay
– Aneuploidy
– Viral infection
Gestational age
Percentile
20 40
255
Gestational age
Percentile
20 40
255
Gestational age
Percentile
20 40
255
Symetrical small
Asymmetrical – small abdomen Asymmetrical – short bones
Fetal growth• Growth is dynamic: single
and serial measurements at >14 day intervals are needed.– Continued growth along
reference ranges is most likely normal.
– measurements that fall off the curve are likely abnormal.
• Abnormal head growth can indicate aneuploidy or viral infection
• Abdominal circumference: single best measure of fetal nutrient status.
• Skeletal growth abnormality: important marker for skeletal dysplasia.
Gestational age
Percentile
20 40
25
5 AC
AC
AC
AC= normal
AC
AC
AC
AC
AC
AC
AC
AC
= abnormal
Amniotic fluid volume• 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
After 14 wks a measure of
- fetal urine production
- placental fluid exchange
Amniotic fluid volume
• ↑ fluid – polyhydramnios– Maternal diabetes
– Tracho-esophageal fistula
– Choanal atresia
– Aneuploidy
– Viral infection
– Tachycardia
– Twin-twin transfusion
• 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 – oligohydramnios
– Rupture of membranes
– Placental insufficiency
– Viral infection
– Aneuploidy
– Urinary obstruction
– 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:– Zoom to the area of
interest
– Apply color Doppler • Narrow color box
• Adjust velocity scale
– Apply pulsed wave gate• Adjust gate to cover
vessel
• Adjust velocity scale
• Adjust filter
– 3-5 uniform waveforms
– No fetal activity
12
34
5
Velocitysystolic peak velocity
end-diastolic peak velocity
atrial systolic peak velocity a
diastolic peak velocity
Dsystolic peak velocity
S
TAMX
TAMX
S
D
Pulsatility index
(S-D)TAMX
TimePulsatility index
(S-a)TAMX
Doppler ultrasound• 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
• 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• Relationship of systole
and diastolic velocity and waveform characteristics depend on– Input pressure
– Vascular resistance
• Vascular resistance may be altered due to– Changes in vessel tone
– Structural vascular change
S
D Input pressure
Vessel tone Vascular histology
Peripheral resistance
AutoregulationMCARenalHepaticAdrenalCoronarie
sSplenic
VasoconstrictionDA after Indomethaci
n
Failed placentationUmbilical
arteriesUterine arteries
Venous Doppler• Venous Doppler gives
information about forward cardiac function– Compliance
– Relaxation
– Contractility
– Afterload
• All vessels have the same waveform– Systolic peak
– Diastolic peak
– Atrial systole
• Clinically most studied– Ductus venosus
– Inferior vena cava
– Umbilical vein
S
D
A
Contractility
Afterload
60 - 70%
Placenta
Compliance
The placenta• A two compartment
nutrient, fluid and gas exchange organ
• Maternal compartment – Uterine artery Doppler.
• Fetal compartment – Umbilical artery Doppler.
• Maturation of the vasculature is observed in both compartments,– Loss of uterine artery
notch
– Appearance of umbilical diastolic velocity
– Successive decline in Pulsatility index in both vessels
• Gestational age is important for assessing waveforms
Maternal compartment
Fetal compartment
11 weeks
11 weeks
24 weeks
24 weeks
40 weeks
40 weeks
500-600 ml/min.
250 ml/Kg/min.
12 m2
The placenta• 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
Umbilical artery
Uterine artery
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
• 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 veinConstant
Fetal behavior1st trimester 2nd trimester 3rd trimester
Activity
Coupling
Cyclicity
Behavioral states
Gross body movement
Breathing movement
Movement & FHR
Glucose & breathing
Vibroacoustic
Rest activity cycles
Stable constellation of activity
• Fetal behavior develops sequentially:– Isolated activity
– Coupling of behavior
– 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
flexion-extension 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.
cerebral cortex
ANS
VMC RAS
Heart CVS
BP = CO peripheral resistancex
HRxstroke volume
Fetal heart rate
• A record of autonomic regulation of intrinsic cardiac activity and its modulation by regulatory centers.– Vasomotor center (VMC)
– Reticular activating system (RAS)
– Autonomic nervous system (ANS)
• Analyzed visually by– Baseline heart rate
– Reactivity
– Variability
– Periodic changes
• 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• Modified BPS
– Amniotic fluid index
– Reactive FHR
• Composite score of 5 variables– Normal = 10, 8
(PNM=1/1000)
– Equivocal (PNM=7-10/1000) • 8 with oligohydramnios
• 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
Tone at least one episode of active limb, trunk or hand extension with return to flexion
Movement
at least 3 discrete body/limb movements (active continuous considered as single movement)
Breathing at least one episode of at least 30 seconds duration (includes hiccups)
Amniotic fluid at least one single vertical pocket >2 cm
Heart rate 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
For each component presence = 2 points, absence = 0 points
pH < 7.10
-10
Δ p
HFHR
parameters
0
-2
-4
-6
-8
NST cCTG* ToneAFV FBM FGM AEDV TAO MCA CPR DVDAO
-reaktiv
LTV <30
STV <3.5
biophysicalparameters
DopplerParameter
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.
pH < 7.20
Breathing
Tone & Movement
biophysical parameter = closer relationship with pH
abnormal cCTG und Ductus venosus comparable pH
SummaryTests provide specific information
Fetal anatomy – differential diagnosis Fetal growth – placental performance Amniotic fluid – volume status / placental transferUterine Doppler – trophoblast invasion
Umbilical Doppler – vascular exchange area
MCA Doppler – pCO2, Hgb, Oxygen, Hypertension
Venous Doppler – rhythm, forward cardiac functionDynamic variables – Maturation, Behavioral state, pO2FHR variables – CNS, PNS, pO2
Specific conditions require specific tests…
Pathways of deterioration
adaptation
Fetal condition
hypoxemia
Stillbirth
compromise
acidemia
» alterations fetal heart rate pattern
» alterations in regional blood flow
» decrease in dynamic variables
» declining amniotic fluid volume
INTERVENTION
Not every condition produces the same clinical
findings with fetal compromise…
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
Delayed behavioral maturation
BP
S
Delayed maturation of FHR control
Increased baselineDecreased variation / variabilityDecreased reactivity
variation decrease / loss
Loss of breathing
declining amniotic fluid volume
declining global activity
Ductus venosus
Umbilical artery
Middle cerebral artery
PLACENTA – BASED GROWTH DELAY
CIRCULATORY COMPENSATION
DEVELOPMENTAL DELAY
* *
DECLINING ACTIVITY
* *
CIRCULATORY DECOMPENSATION
CIRCULATORY COMPROMISE
Loss of movement
Loss of tone
ABNORMAL BPS
Δ p
H
0
- 4
- 6
- 2 HYPOXEMIA ACIDEMIA STILLBIRTH
Baschat 2008
FGR after 34 weeks
Ductus venosus
Umbilical artery
Middle cerebral artery
Nonreactive heart rate
Loss of breathing
declining amniotic fluid volume
Δ p
H
0
- 4
- 6
- 2
Baschat 2008?
PLACENTA – BASED GROWTH DELAY
STILLBIRTH
Likely diagnosis
Anatomy
Amniotic fluid
Aneuploidy
Syndrome
Viral infection
normal
normal or decreased
Umbilical artery Doppler
normal
Middle cerebral artery Doppler
normal
Cerebroplacental ratio
normal
abnormal
increased
elevated indexAbsent / reversed end-diastolic velocity
decreased index
decreased ratio
IUGR due to placental insufficiency
normal repeat examination at 14 days
Constitutionally small fetus
Approach to the fetus with small biometry
The principal decisions
The monitoring interval
Which thresholds to base delivery on ?
Early stages require less frequent monitoring
Disease acceleration = ↑ monitoring frequency
New onset brain sparing
Abnormal DV Doppler
Oligohydramnios
UA – AEDV / REDV
Early gestation = high threshold
Late gestation = low threshold
Turan OM et al., Ultrasound Obstet Gynecol 2008
27 29 31 33 35 37 39
Degre
e o
f D
opple
r A
bn
orm
alit
y
Gestational weeks
Severe
Progressive
Mild
↑ UA PI
↓ Cerebroplacental Doppler ratio
UA A-REDVBrain sparing
Abnormal DV index
DV RAV – UV pulsations↑ UA PI
↓ Cerebroplacental Doppler ratio
Brain sparingUA A-REDV
Abnormal DV index
DV RAV – UV pulsations
↑ UA PI
↓ CPR
46 day latency / 35.3 weeks delivery
38 day latency / 33.4 weeks delivery
27 day latency30 weeks delivery
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
Neonatal survival
24 25 26 27 28 29 30 31 32
Gestational week
0
10
20
30
40
50
60
70
80
90
100Perc
en
t
Intact survival
2% / day in utero
1%/day in utero
Baschat et al., Obstet Gynecol 2007
N=642
Overall mortality = 130 (21%)
Intact survival = 352 (54%)
Prospective Stillbirth rate
0
0.5
1
1.5
2
2.5
24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
Ris
k /
10
00
on
goin
g p
reg
nan
cie
s
prospective stillbirth rate
prospective perinatal mortality rate
Kahn et al., Obstet Gynecol, 2002
Favor delivery
for singleton
s
• 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 !
0
20
40
60
80
100
24 25 26 27 28 29 30 31 32
Perc
en
t on
goin
g p
reg
nan
cie
s
Gestational week
modified BPP & AREDV
Abnormal BPP alone
DV RAV or UV Pulsations and absent movement or fluid
19/29 stillbirths prevented18/30 Acidemia prevented28.5 weeks delivery GA8% increase in survival
18/29 stillbirths prevented17/30 Acidemia prevented29.3 weeks delivery GA15% increase in survival
11/17 stillbirths prevented12/ 24 Acidemia prevented28.0 weeks delivery GA
Combined tests – hypothetical modeling
Baschat et al., AJOG 2007
Intervention triggers
24 26 29 32 34
individualize
STV < 3.5 msec
DV - RAV
STV < 4 msec
DV PI > 3SD UA - REDV UA-AEDV
Biophysical profile score < 6
Integrated fetal testing score < 8
Periviability Steroids beneficialNot well
delineated
Greatest survival benefit / day in utero
TRUFFLE
Baschat 2008
Maternal Diabetes
Pregnant
Non-pregnant
60
70
80
90
100
110
120
130
140
0
50
100
150
200
250
8 10 12 14 16 18 20 22 24 2 4 6 8
IU /
ml
mg
/dl
GLUCOSE
INSULIN
Increased insulin resistance
Higher postprandial glucose
Lower fasting glucose
Potential risk to develop diabetes in pregnancy
Risks of worsening glycemic control in existing diabetes
Diagnosis
Fasting sugar
1’ sugar
Therapy
Whites Class
Current pregnancy
<105 mg%
<140 mg%
>105 mg%
>140 mg%
Diet Insulin
A 1 A 2
Duration
Vascular risks
Insulin
> Age 20
<10 years
B
Age 10-19
10-19 years
C
Age<10
>20 years
Benign Retinopat
hy
D
Nephro-pathy
Proliferative
Retinopathy
Cardiac
F R H
Pregnancy risks
PIH / PET
Maternal Mortality
Fetal death
Anomalies
Macrosomia IUGR
Surveillance in diabetes
• Signs of glycemia-mediated risks– Macrosomia
– Polyhydramnios
– Myocardial thickening
• Signs of vascular-mediated risks– IUGR
– Abnormal uterine artery Dopplers
Monitor fluid & FHR Monitor like IUGR
Once / twice weekly Once / twice weeklyEmpiric monitoring based on GA
Start monitoring in the presence of above signs
Anti Ro/La antibodies• 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
MV
AAO
A
E
Fetal SVT• 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
Reappearance of normal venous pattern
Cardioversion
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 - pathophysiologyAlterations 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
Cardiac disease
Structural problems
Anemia-related issues
MCA PSV
Venous Doppler
Prognosis
>70 % mortality
Doppler in Hydrops
Critical diagnostic tool
Prognostic assessment
Allows for monitoring of potentially treatable lesions – CCAM, Sacrococcygeal Teratoma
Post-dates pregnancy• Correct routine first
trimester ultrasound dating almost halves rates of post-term 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– Twice weekly
surveillance
• Induction at 41 weeks decreases stillbirth rate significantly.
0
0.5
1
1.5
2
2.5
24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
Ris
k /
10
00
on
goin
g p
reg
nan
cie
s
prospective stillbirth rate
prospective perinatal mortality rate
Kahn et al., Obstet Gynecol, 2002
Favor delivery
for singleton
s
Conclusion
Surveillance should be disease specificTesting frequency should be based on disease acceleration
Intervention thresholds should be based on intrauterine versus neonatal risks