Umbilical artery doppler provides a non-invasive way to assess fetal circulation. Abnormal findings in the umbilical artery doppler such as absent or reversed end diastolic flow indicate placental insufficiency and fetal hypoxia. As the condition worsens, there is a progression from reduced to absent to reversed end diastolic flow. Along with other tests such as MCA and ductus venosus doppler, umbilical artery doppler helps predict poor fetal outcome if no interventions are made.

1. Umbilical artery doppler [1]
Dr. Kamal Sayed MBBS MSc US UAA

2. INTRODUCTION
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Non-invasive assessment of circulation
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• Fetal circulatory system
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• Umbilical artery
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• Umbilical vein
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• Aorta
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• Heart
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• Middle cerebral artery

3. Dopp Equation : fd = 2 ft v/c
fd {dopp freq} / ft [transmitted freq] / v [sound speed]/ c [blood velocity]
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Physics of doppler ultrasound
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• Refers to the change in frequency wave transmission [ft]
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when motion occurs b/w source of wave transmission &
observer [rf].
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Dopp sfift frequency [fd] = [ft-fr]
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• 1] US beam into 2] circulating blood 3] million red cell
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4] speed red cell movement [velocity of blood flow{c}].
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Speed of sound [v]
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Dopp Equation : fd = 2 ft v/c
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Slide [4]
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5. •
Modalities of Doppler Ultrasound
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Implementation for assessing circulation:
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- Continuous wave ( CW )
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- Pulsed wave ( PW )
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- Color doppler ( CFD )

6. •
Pulse wave : @ Vascular location. @ Interrogation deep
vessel. Slide [7]
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Continuous wave : @ Determining and monitoring fetal
heart rate. @ Cannot identify exact location. Slide [8]
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Color flow : @ estimation of mean doppler shifted
frequency.
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@ real time of 2 dimensional of anatomic structures.
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@ Provide qualitative hemodynamic information
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@ Presence and direction of blood flow.
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Slide [9]
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•

8. CW of umbilical blood flow interrogation site umbilical arterial flow.
Vertical axis show flow velocity ED flow low impedance in feto-placental arterial
circulation.

10. •
Doppler waveform Analysis
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• Reflect blood velocity in circulation.
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• Presence and direction of flow
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• Volume of flow
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• Impedance
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• Peak systolic frequency ( S )
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• End- diastolic frequency ( D )
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• Average frequency shift value over the cardiac cycle ( A )
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Slide [11]
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12. •
The commonly used obstetrical applications :
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1* (S/D) ratio = Peak systolic frequency shift TO end-diastolic
frequency shift : [PSV/EDV].
•
2*(RI) Resistance index : Is the difference between peak
systolic and end diastolic shift, divided by peak systolic shift
[PSV – EDV / PSV].
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3* (PI) Pulsatility index : is the difference between PSV & EDV
divided by the time- average flow velocity
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PI = (vmax - vmin) / (vmean)
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# higher PI is associated with higher downstream vascular
resistance.

13. •
# UA doppler reflects resistance in the fetal side of the
placenta.
•
# Uterine artery doppler reflects resistance in the maternal
side of the placenta.
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# MCA doppler reflects redistribution of blood flow.
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# a simple Rule to remember :
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UA S/D ratio should be under 3.0 [mean 2.5] after 30 wks
gestation.
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Slide [14/15]

16. •
Factor affecting the waveform
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Gestational age
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1- EDV increase with gestation.
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2- Decline in feto-placental blood flow impedance
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3- Decline S/D Ratio and RI.
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# there is relative increase in diastolic forward flow with later
gestational ages [a smaller S/D ratio with advancing age]
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# it normal to have absent ED flow in the 1ST & very early 2ND
trimester.
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slide [17]
•
•

17. Normal UA doppler waveform with advancing gestational age.

18. •
Fetal circulation
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*Umbilical cord Connects placenta to fetus.
*oxygenated blood moves to the fetal circulation.
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*Umbilical vein Carries oxygenated blood from the placenta to
the fetus.
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* Fetal circulation pathway :
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*placenta
* umbilical vein
* ductus venosus ( shunt 1, : shunts blood away from the
fetus' liver)
* inferior vena cava (oxygenated blood mixes with venous)
* right atrium thru foramen ovale ( shunt 2)

19. •
* some blood flows to the right ventricle to the lungs
* ductus arteriosus ( shunt 3) shunts blood away from fetus
lung to the aorta
* left atrium (blood from pulmonary veins and foramen ovale)
to left ventricle to aorta
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Name the 3 shunts in the fetal circulation pathway ?
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1) ductus venosus
2) foramen ovale
3) ductus arteriosus

20. •
*Ductus venosus shunts (#1) blood Away from the fetus' liver.
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*Foramen ovale shunts (#2) opens to the Right and left atrium
Moves blood to right and left atrium
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*Ductus arteriosus shunts (3) Blood away from the fetus lung
to the aorta.
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Why do fetus have shunts ?
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Because that organ is not in use
[Liver and lung]

21. •
*Tearing of the uterine wall [Placenta abruptia].
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*Placenta previa [Is when the placenta is delivered before the
fetus].
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Outcome of placenta problems :
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* Fetal asphyxia
* increased risk of brain damage
* respiratory distress in immediate post natal period
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22. Fetal circulation

23. •
Arterial PWD pulsatility/resistance
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1- low resistance & low pulsatility : brain & renal bed flow.
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2- high resistance high pulsatility : peripheral arterial.
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The pulsatility index (PI) (also known as the Gosling index)
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is a calculated flow parameter in ultrasound, derived from the
maximum, minimum, and mean Doppler frequency shifts
during a defined cardiac cycle.
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Along with the resistive index (RI), it is typically used to
assess the resistance in a pulsatile vascular system.
•

24. •
The pulsatility index is the difference between systolic flow
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velocity and diastolic flow velocity, divided by the time-
averaged flow velocity, and is related to downstream vascular
resistance (higher pulsatility index is associated with higher
downstream vascular resistance).
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PULSATILITY INDEX : PI = (vmax - vmin) / (vmean)

25. •
Umbilical artery (UA) Doppler indices, i.e., pulsatility
index (PI), resistance index (RI), and systolic/diastolic ratio
(S/D) calculated from blood flow velocities, are used as an
important clinical tool for evaluating fetal wellbeing in high-
risk pregnancies and to predict outcome of growth restricted
fetuses.
•
The purpose of this study was to determine the
range, mean and standard deviations of pulsatility index (PI),
resistance index (RI) and systolic/diastolic (S/D) ratio of the
uterine artery at 22nd & 23rd weeks of pregnancy with
normal as well as those with abnormal outcome.

26. •
What is normal umbilical artery Doppler?
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@ The umbilical arterial waveform usually has :
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1- a "sawtooth" pattern
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2- with flow always in the forward direction, that is towards
the placenta.
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@ An abnormal UA waveform shows :
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Absent OR reversed diastolic flow.
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[Before the 15th week, the absence of diastolic flow may be
a normal finding.]
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Slide [18]

27. Normal Umbilical Artery Doppler

28. Color doppler in fetal hypoxia

29. https://line.17qq.com/articles/lpghpdppv_p6.html

30. LT upper : normal pregnancy/ RT upper : reduced EDV /
LT lower : absent EDV / RT lower : reversed EDV

31. •
Uterine artery PI provides a measure of uteroplacental
perfusion and high PI implies impaired placentation with
consequent increased risk of developing @ preeclampsia,
@fetal growth restriction, @ abruption @ and stillbirth.
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The uterine artery PI is considered to be increased if it is
above the 90th centile.
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Low-dose aspirin [LDA] and omega-3 fatty acids improve
uterine artery blood flow velocity in women with recurrent
miscarriage due to impaired uterine perfusion .

32. •
Umbilical arterial (UA) Doppler assessment is used in
surveillance of fetal well-being in the third trimester of
pregnancy. Abnormal umbilical artery Doppler is a marker
of placental insufficiency and consequent intrauterine growth
restriction (IUGR) or suspected pre-eclampsia.
•
Umbilical artery Doppler assessment has been shown to
reduce perinatal mortality and morbidity in high-risk obstetric
situations.

33. •
The spectral Doppler indices measured at the fetal end, the
free loop, and the placental end of the umbilical cord are
different with the impedance highest at the fetal end.
•
The changes in the indices are likely to be seen at the fetal
end first.
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Ideally, the measurements should be made in the free cord,
however, for consistency of recording in cases being followed
up, a fixed site would be more appropriate, i.e. fetal end,
placental end, or intra-abdominal portion.
•
Due to difficulty with measuring the cord at the fetal end in
many IUGR fetuses, measurement in a free loop is
acceptable .

34. •
The 95% confidence interval limit slowly decreases for both
the resistive index (RI) and pulsatility index (PI) through the
course of gestation due to progressive maturation of the
placenta and increase in the number of tertiary stem villi.
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The Doppler indices have been found to decline gradually
with gestational age (i.e. there is more diastolic flow as the
fetus matures):
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S/D ratio mean value decreases with fetal age at 20 weeks,
the 50th percentile for the S/D ratio is 4
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at 30 weeks, the 50th percentile is 2.83
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at 40 weeks, the 50th percentile is 2.18
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35. •
RI mean value decreases from 0.756 to 0.609
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PI mean value decreases from 1.270 to 0.967
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Classification of severity
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1- In IUGR fetuses AND fetuses developing intrauterine
distress, the UA blood velocity waveform usually changes in
a progressive manner as below :
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@ reduction in end-diastolic flow : increasing RI values, PI
values, and S/D ratio
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@ absent end-diastolic flow (AEDF): RI = 1
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@ reversal of end-diastolic flow (REDF)

36. •
2- Abnormal UA Doppler is an indication of further
sonographic workup of the degree of placental insufficiency:
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@ fetal MCA Doppler assessment
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@ ductus venosus flow assessment
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@ umbilical venous flow assessment
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3- Change in blood flow impedance in fetal regional
circulation underlie this phenomenon.
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4- Doppler shows circulatory changes associated with fetal
compromise and perinatal prognostication.
•
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Slide [37]

38. Normal UA waveform

39. IUGR [UA]

40. •
Sequence changes in FHR, doppler findings, biophysical
parameters
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1- reflect fetal homeostatic response to chronic hypoxia.
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2- Abnormal elevation of doppler : @ precede loss of
variability and reactivity.
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3- leading to decline and loss of fetal breathing and
movements.

41. POOR OUTCOME!
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“Death occurs if there are no interventions” when :
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1- Reversed end diastolic velocity in the umbilical artery
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2- Absence or reversed atrial wave in the ductus venosus.
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3- Rapid Loss of hear rate variability.

46. •
Doppler velocimetry of UA provide a noninvasive measure of
the fetopacental hemodynamic state.
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• UA Doppler reflect impedance of downstream circulation
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• Abnormality of doppler correlated to fetoplacental vascular
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maldevelopment (Fetal hypoxia, fetal acidosis and adverse
perinatal outcome).
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• In Pregnancy complicated by fetal growth restriction or
preeclampsia at >34 wga result in AEDV or REDV which will
recommend prompt delivery rather than expectant
management.
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•