Doppler us in the evaluation of fetal growth

2.  Diagnose fetal growth restriction.
 Current obstetric literature regarding the use
of Doppler velocimetery surveillance in
suspected fetal growth restriction.
 Techniques for acquiring Doppler waveforms
of the umbilical artery, MCA, and ductus
venosus.

3.  American Congress of Obstetricians and
Gynecologists (ACOG) --- EFW below the
10th percentile for gestational age.*
 The Royal College of Obstetricians and
Gynecologists -- abdominal circumference
below the 10th percentile alone meets the
criteria for growth restriction.

4. Adverse outcomes associated with IUGR
 Increased risks of intrauterine demise
 Neonatal morbidity
 Neonatal death

5.  Hadlock et al. --- Four standard US
measurements.
 The International Fetal and Newborn Growth
Consortium for the 21st Century
(INTERGROWTH-21st) --- five US
measurements

6.  The accurate diagnosis of a growth-restricted
fetus requires an accurately assigned estimated
due date (EDD).
 LMP
 For patients with uncertain or unreliable
menstrual dating, first-trimester US is the most
accurate method for determining EDD.*

7.  If a patient presents for a first prenatal visit in
the second or third trimester with uncertain or
unreliable menstrual dating, EDD should be
calculated using biometric parameters.

8.  Maternal (chronic conditions)
 Fetal
 Placental
 Eventually causing suboptimal uterine-
placental perfusion and fetal nutrition.

9.  Guide pregnancy management decisions,
including the timing of delivery.
 Umbilical artery Doppler --- valuable in
predicting perinatal outcomes.

10.  Changes first appear in umbilical artery
followed by MCA.
 Then alteration in venosus circulation,
including ductus venosus and umbilical vein.*

11.  PSV
 S/D RATIO
 RI
 PI

12.  Suspected fetal growth restriction
 Resistance of blood perfusion in the
fetoplacental unit and is the primary
surveillance tool for fetuses with growth
restriction.

14. The Doppler indices have been found to decline
gradually with gestational age:
 S/D ratio mean value decreases from 3.560 to
2.511
 RI mean value decreases from 0.756 to 0.609
 PI main value decreases from 1.270 to 0.967

16.  Maternal or placental conditions that obliterate
small muscular arteries in the placental villi*
result in:
a) progressive decrease in end-diastolic flow
b) absent
c) then reversed

17.  Strong association with adverse perinatal
outcomes* in growth-restricted fetuses
 Pulsatility index (PI) greater than the 95th
percentile or as absent or reversed end-
diastolic flow. **

18.  * Doppler waveforms of the umbilical artery
can be obtained from any segment along the
umbilical cord.
 SMFM recommends -- at the abdominal cord
insertion.
 ISUOG -- at the free loop of the umbilical
cord for simplicity and consistency, exception
to this would be in a case of multiple
pregnancies.

19.  The systolic-to-diastolic ratio and PI should be
obtained in the absence of fetal breathing.*
 If abnormal waveforms are obtained ensure
that maternal positioning is not responsible for
the abnormality.

20.  The fetal brain in normal pregnancies has
high resistance circulation with continuous
forward flow that is present throughout the
cardiac cycle.
 MCA waveforms can be obtained to measure
the PSV, EDV and PI.

23.  An axial image of the fetal head is obtained at
the level of the sphenoid bone, and the
transducer is angled until the circle of Willis is
visualized.
 A 2-mm pulsed wave Doppler gate is placed at
the proximal third of the MCA, angle of
insonation kept as close to 0° as possible

25.  Pulsed Doppler US parameters are generated
from three or more consecutive waveforms.
 Highest point ---PSV in cm/s

26.  Fetal hypoxemia -- a phenomenon of blood
flow redistribution occurs.*
 To compensate for the decrease in available
oxygen.
 Increased EDV in the MCA, which is reflected
as a low PI.

27.  The MCA PSV has also been studied in the
setting of fetal growth restriction.
 At this time, there is not enough evidence that
MCA Doppler US alone is useful for
informing decisions about the timing of
delivery in fetal growth restriction.

28.  Predictor of adverse pregnancy outcomes in
the setting of fetal growth restriction.
 Assessment of fetal brain sparing
 MCA PI/ UMB A PI*
 Fetal brain sparing < 5th percentile for GA**

29.  With IUGR/hypoxia up to 70% of flow is
shunted to brain/coronaries
 MCA Diastolic flow increases - SD ratio
decreases
 UA SD ratio increases as placental resistance
increases
 Eventually UmA SD ratio > MCA SD ratio =
“brain sparing" pattern

30.  In growth retarded fetus the disappearance of
the brain sparing effect or presence of reversed
MCA flow is a critical event for the fetus and
precedes fetal death.

31.  First-trimester screening for aneuploidic
anomalies.
 Second-trimester scanning when there are
concerns regarding
 intrauterine growth restriction (IUGR)
 fetal cardiac compromise

33.  Sampling is done where the umbilical vein
joins the ductus venosus
 A right ventral midsagital view of the fetal
trunk should be obtained
 The probe is ideally angled to allow a mid
sagittal plane or a transverse oblique plane
through the fetal abdomen
 The Doppler sample should be small (0.5-1
mm)
 The insonation angle should be 30°

36.  Decreased, absent, or reversed flow in the A
wave -- increased right ventricular after load.
 An absent or reversed ductus venosus A wave
-- a sign of impending acidemia or death,
usually within 7 days.

37.  Before 32 weeks, delaying delivery until
abnormalities are seen at ductus venosus
Doppler US or cardiotocography is “probably
safe and possibly benefits long-term outcome”
in survivors.

38.  EFW below the 10th percentile for gestational
age is the most commonly used definition of fetal
growth restriction, it is not without controversy.
 US surveillance with umbilical artery Doppler to
identify fetuses most at risk for poor outcome and
to guide timing of delivery.
 The use of other Doppler waveforms (MCA,
CPR, and ductus venosus) in the setting of fetal
growth restriction remains investigational.