Summary of OBSTETRIC DOPPLER

1. Obstetric Doppler
DR LAXMI NARAYAN SHARMA
DR RAHUL PARMAR

2. Contents
• DOPPLER EFFECT
• Application in Ultrasound
• Doppler ultrasound
• Indications
• Methodology of Doppler assessment of the
placenta and fetal circulation
• General Precautions
• Conclusion of study and correlation

3. • Change in frequency of a wave for an observer
moving relative to the source of wave.
A. As the wave source moves towards the observer
Each successive wave crest is emitted from a position closer than the previous wave ,
each successive wave takes less time to reach the observer than the previous results
in increase in frequency
B. Conversely as the wave source move away from the observer
Each successive wave crest is emitted from further away from the observer , thus
each successive wave takes longer to reach the observer and frequency decreases.

4. Application in Ultrasound
• BASIC PRINCIPLES
• Ultrasound images of flow, whether color flow or spectral Doppler, are
essentially obtained from measurements of movement.
• In ultrasound scanners, a series of pulses is transmitted to detect
movement of blood. Echoes from stationary tissue are the same from
pulse to pulse. Echoes from moving scatterers exhibit slight differences in
the time for the signal to be returned to the receiver.
• These differences can be measured as a direct time difference or, more
usually, in terms of a phase shift from which the ‘Doppler frequency’ is
obtained .
• They are then processed to produce either a color flow display or a
Doppler sonogram.

5. Doppler Ultrasound
• Continuous wave Doppler ultrasound
• Pulsed Doppler (Spectral Doppler)
• Color flow imaging
FLOW TOWARD THE TRANDUCER : RED
FLOW AWAY FROM THE TRANDUCER : BLUE
• Power Doppler (information of amplitude)

6. • Figure 3: Effect of the Doppler angle in the sonogram. (A) higher-frequency
Doppler signal is obtained if the
• beam is aligned more to the direction of flow. In the diagram, beam (A) is more
aligned than (B) and
• produces higher-frequency Doppler signals. The beam/flow angle at (C) is almost
90° and there is a very poor
• Doppler signal. The flow at (D) is away from the beam and there is a negative
signal

7. Indications
• Investigation of the uterine and umbilical arteries
gives information on the perfusion of the utero
placental and feto placental circulation
respectively.
• IUGR assessment in second and third trimesters.
• In fetal distress and Fetal insufficiency
• Doppler studies of selected vital organs are
valuable in assessment of hemodynamic
responses on fetal hypoxia and anemia
• Color doppler plays important role in diagnosis of
cardiac and non cardiac malformations.

8. Indication for assessment of the
uterine artery doppler ultrasound
• Previous history of pre eclampsia
• Previous child with IUGR
• Unexplained high maternal serum alpha feto
protein
• High HCG levels
TIMING OF DOPPLER :
As and when the clinician suspects
As and when the growth of fetus is not proportional
to weeks of gestation.

9. Methodology of Doppler assessment
of the placenta & fetal circulation
Factors affecting flow velocity waveform
1. Maternal position : Semiremcubent, with slight lateral tilt
2. Fetal heart rate :inverse relation between FHR and cardiac cycle .
When heart rate drops end diastolic frequency shift decline and vice versa
3. Fetal breathing movements : conduct during fetal
apnea and absence of fetal hiccups
4. Blood viscosity : increase Blood viscosity is associated with
decrease cardiac output

10. Technique of Fetal Doppler
• Fetal Doppler is carried out on both arterial and
venous flow , 3 sets of reading are taken before
final values are given
• Each sample have at least 3 wave cycles
• Angle independent indices are
1. Systolic to diastolic ratio (S/d Ratio)
2. Resistive index (RI)= (PSV-EDV)/PSV
3. Pulsatility index (PI)= (PSV-EDV)/Mean velocity

11. Cereberoplacental Ratio
• CPR is an Ultrasound tool used as predictor of
adverse pregnancy outcome in both small for
gestation age and appropriate for gestational
age fetuses.
• An abnormal CPR reflects redistribution of
cardiac output to the cerebral circulation and
associated with Intrapartum fetal distress.
• CPR = MCA PI / UA PI
• CPR <5th percentile is considered abnormal

12. • TABLE 48-1. FACTORS THAT CHANGE
RESISTIVE INDEX (RI) FACTOR EFFECT ON RI
• High-pass filter settings Increased
• Scanning pressure Increased
• Patent ductus arteriosus Increased
• Elevated heart rate Decreased
• Decreased cardiac output Decreased

13. Uteroplacental circulation
• ANATOMY : The blood supply to the uterus comes mainly from the
uterine arteries, with a small contribution from the ovarian
arteries.
• These vessels anastomose at the cornu of the uterus and give rise
to arcuate arteries that run circumferentially round the uterus.
The radial arteries arise from the arcuate vessels and penetrate at
right angles into the outer third of the myometrium.
• These vessels then give rise to the basal and spiral arteries, which
nourish the myometrium and decidua and the intervillous space
of the placenta during pregnancy, respectively.
• There are about 100 functional openings of spiral arteries into the
intervillous space in a mature placenta, but maternal blood enters
the space in discrete spurts from only a few of these.

14. METHODOLOGY OF OBTAINING
WAVEFORMS
• UTERINE ARTERY : BRANCH OF ANTERIOR
DIVISON OF INTERNAL ILIAC ARTERY ARISING
BELOW OBTURATOR ARTERY

15. • CAMPBELL et al uses continous wave doppler usg
obtained waveform from arcuate arteries
• Trudinger et al uses continous wave doppler usg
obtained waveforms from branches of uterine
arteries in the placental bed
• Schulman et al uses continuous wave Doppler usg
to locate Uterine artery in the Para uterine region
in the lower uterine segment and rotated till
characteristic waveform was recogznised

19. Abnormal waveform of Uterine Artery
• If the end diastolic flow does not increase
throughout pregnancy or if a small notch is
detected at the beginning of diastole , the fetus
is at high risk of developing IUGR .
• Diastolic blood flow may be absent or even
reversed with degrees of placental dysfunction ,
such finding may result into fetal death
• An abnormal PI and uterine artery notching in the
second trimester best predicated pre eclampsia ,
where as predicator of IUGR in high risk patient
was increased RI

20. Umbilical Artery
• It was the first vessel to be evaluated by
Doppler Velocimetry
• Saw tooth appearance of the arterial flow in
one direction and continuous umbilical
venous flow in other
• Free floating portion of the cord is identified
and the Doppler sample volume is placed over
an artery and vein.

23. Abnormal waveform of Umbilical
Artery
• Decreased diastolic component and angle
independent indices became abnormal (values
above reference range) , this occurs in IUGR
• Worsening of placental insufficiency result in
decrease in diastolic velocity which then
becomes absent and later reversed
• The values of various indices are variable with
age and should be correlated with charts.

26. Cerebral arteries
• With the color Doppler technique, it is possible to investigate the main
cerebral arteries such as the internal carotid artery, the middle cerebral
artery, and the anterior and the posterior cerebral arteries and to
evaluate the vascular resistances in different areas supplied by these
vessels.
• A transverse view of the fetal brain is obtained at the level of the
biparietal diameter. The transducer is then moved towards the base of
the skull at the level of the lesser wing of the sphenoid bone.
• Using color flow imaging, the middle cerebral artery can be seen as a
major lateral branch of the circle of Willis, running anterolaterally at the
borderline between the anterior and the middle cerebral fossae.
• The pulsed Doppler sample gate is then placed on the middle portion of
this vessel to obtain flow velocity waveforms.
• Due to the course of this blood vessel, it is almost always possible to
obtain an angle of insonation which is less than 10°.
• During the studies, care should be taken to apply minimal pressure to
the maternal abdomen with the transducer, as fetal head compression is
associated with alterations of intracranial arterial waveforms

27. Middle cerebral artery
• Location and technique : Obtain axial section of the head at the level of
sphenoid bones, identify circle of Willis with MCA.MCA should be sampled as soon after its origin.
• Normal variants in MCA
1. MCA PI changes throughout gestation
2. The lower PI values in early and late in gestation
may result from the increased metabolic
requirement of the brain during these period.
3. Reversed flow of MCA velocity waveforms can
be observed with head compression in normal
pregnancies

32. Abnormal findings of MCA
• IUGR is associated with increased blood flow to
the fetal brain, this is visualized as increased
blood flow during diastole on Doppler this effect
is known as Brain sparing effect and is
demonstrated by lower value of MCA PI.
• MCA is below the normal range when the oxygen
tension (po2) is reduced.
• When O2 deficit is greater the PI tends to rise ,
suggesting development of Cerebral edema

33. Cont..
• In IUGR fetuses the disappearance of the brain sparing
effect or presence of reversed MCA flow is critical
event and precedes Fetal death
• MCA PSV is increased in IUGR , predicts perinatal
mortality than the MCA PI
• In Anemic fetuses , The high MCA PSV is related to
decreased fetal hemoglobin that can decrease blood
viscosity therefore cardiac output increases.
• In IUGR fetuses however the MCA PSV increases
significantly related to hypoxemia and hyercapnia and
thus brain autoregualtion

34. Descending aorta
• Velocity waveforms from the fetal descending aorta are usually recorded at the
lower thoracic level just above the diaphragm, keeping the angle of insonation of
the Doppler beam below 45°.
• Diastolic velocities are always present during the second and third trimesters of
normal pregnancy, and the pulsatility index (PI) remains constant throughout
gestation.
• Flow velocity waveforms in the descending aorta represent the summation of
blood flows to and resistance to flow in the kidneys, other abdominal organs,
femoral arteries (lower limbs) and placenta.
• Approximately 50% of blood flow in the descending thoracic aorta is distributed
to the umbilical artery. With advancing gestation, the PI in the umbilical artery
decreases, due to reduced resistance in the placental compartment, whereas, in
the aorta, the PI remains constant.
• The absence of a change in PI suggests the presence of a compensatory
vasoconstrictive mechanism in the other major branches of the aorta
distribution, such as the extremities. The mean blood velocity increases with
gestation up to 32 weeks and then remains constant up to 40 weeks, when there
is a small fall

35. Continued..
• Measured at the level of diaphragm
• The PI of the fetal descending aorta is 1.96+/-
0.30(SD) at the diaphragm & 1.68+/-0.28 after
the origin of Renal Arteries.
• Waveforms represent the summation of flow
to the kidneys , bowel , placenta and the
lower extremities
• In severe IUGR , there is reversed flow in the
descending aorta.

39. General Precautions
• 1- identify the vessel of interest is to be taken utmost care
• 2- TGC, PRF, depth, zoom, gain and brightness, frequency to
be adjusted at every moment
• 3- common artifacts maybe aliasing, pseudo flow, color
bleed, Mirror image, spectral volume artifact, spectral
broadening and gain
• 4- Marker of continuous wave Doppler always to be placed
in the middle of the flow
• 5- anomalies such as single umbilical artery, aberrant ICA,
aberrant subclavian, loop around neck ( CAN) congenital
strictures and stenosis, anastomosis malformations be
easily ruled out with Doppler studies

40. Conclusion of study and correlation-
1- we need to correlate the PI RI and SD ratio
with calculator available
2- finding above 95th percentile and below 5th
centile is indicated for urgent intervention
3- findings rather between 5th to 95th
percentile are to be correlated with partograph
biophysical profile and Bishop scoring and
patient to be monitored for either active phase
or action phase

41. Grading of IUGR

42. IUGR - Medicina Fetal Barcelona