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Doppler us in the evaluation of fetal growth
1.
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.*
12. Suspected fetal growth restriction
Resistance of blood perfusion in the
fetoplacental unit and is the primary
surveillance tool for fetuses with growth
restriction.
13.
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
15.
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.
21.
22.
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
24.
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
32.
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°
34.
35.
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.
Editor's Notes
*The definition recommended by the ACOG indicates that 10% of infants in any population will have a birth weight at or below the 10th percentile. This definition is problematic in that it includes normally grown fetuses at the lower end of the growth spectrum, as well as those with pathologic conditions in which the fetuses fail to achieve their inherent growth potential.
*Antenatal detection and surveillance with delivery timing optimization are necessary to improve pregnancy outcomes
*Once an embryo is visible, the accuracy of gestational age estimation decreases with advancing gestational age; therefore, the EDD should be determined and documented as early as possible.
If the US EFW is below the 10th percentile for gestational age, an accurate EDD should be verified. Once this has been verified, the underlying
cause for the growth restriction should be determined, as the clinical management decisions, outcome, and counseling options are largely dependent on its cause.
AFI, FETAL MOVEMENT AND ANATOMIC SURVEY IF NOT PERFORMED PREVIOUSLY
Once fetal growth restriction has been diagnosed, serial US for the evaluation of fetal growth and Doppler velocimetry are used to
Doppler US of the ductus venosus and MCA provides information about the hemodynamic status of a growth-restricted fetus, but the clinical utility of the interrogation of these vessels has not yet been established
RI = measure of pulsatile blood flow that reflects the resistanceto blood flow caused by microvascular bed distal to the site of measurement.
PI = a measure of the variability of blood velocity in a vessel
*hypertension, diabetes, thrombophilia, and confined placental mosaicism
composite of intraventricular hemorrhage,*periventricular leukomalacia, hypoxic ischemic encephalopathy, necrotizing enterocolitis, bronchopulmonary dysplasia, sepsis, or death
**Conversely, adverse perinatal outcomes are uncommon in growth-restricted fetuses with normal results at umbilical artery Doppler velocimetry.
Multiple randomized trials have shown that the surveillance of growth-restricted fetuses with umbilical artery Doppler US can reduce perinatal death and avoid obstetric interventions
*which is generally visualized as episodic and irregular between episodes of apnea
important part of assessing fetal cardiovascular distress, fetal anaemia or fetal hypoxia
*Blood redistributed to the brain, heart, and adrenal glands at the expense of the peripheral circulation.
*alterations in blood flow to the brain caused by increased diastolic flow due to hypoxia-induced cerebrovascular dilatation and increased placental resistance, resulting in decreased diastolic flow of the umbilical artery.
**Fetuses with growth restriction and an abnormal CPR, born at term, have been shown to be at higher risk for deficits in cognitive functioning and academic achievement at 6–8 years of age
normal Doppler waveform is characteristically biphasic. The first peak is the highest and corresponds to ventricular systole (S wave). The second peak is the second highest and corresponds to early ventricular diastole (D wave), which is followed by a nadir in late diastole that corresponds to the atrial contraction (A wave).