This document discusses the role of color Doppler ultrasound in antepartum fetal surveillance. It begins by outlining the purposes of fetal surveillance, which include reducing fetal death and optimizing delivery timing. It then discusses various maternal and fetal conditions that require increased surveillance due to risks of chronic hypoxia. The document covers different methods of antepartum surveillance and provides detailed explanations of Doppler ultrasound principles, techniques like uterine and umbilical artery Doppler, and how abnormal Doppler readings can predict complications like fetal growth restriction.

1. THE ROLE OF
COLOR DOPPLER ULTRASOUND
IN
ANTEPARTUM SURVEILLANCE
(DR BHARTI GAHTORI)

2. ANTEPARTUM FETAL SURVEILLANCE
The purpose of obstetric care is to optimize maternal and fetal safety
The aim of fetal surveillance is to-
- Reduce the incidence of fetal death through detection of
hypoxic or acidemic infant .
- Minimise the morbidity by optimizing the timing of delivery
- Identify the fetus that are genuinely at risk of chronic
hypoxia and avoid unnecessary intervention in those that are
not .
- Identify those fetus that are at greater risk of acute hypoxia
in labour
-To act as screening as well diagnostic modality to detect the
influence of maternal, placenta & fetal factor on the fetus and
guide regarding frequency of follow up & timely
intervention.

3. WHO ARE THE NEEDY ONES
MATERNAL AND/OR FETAL CONDITIONS AT RISK OF CHRONIC
HYPOXIA ARE-COMMON
MATERNAL INDICATIONS:
-Hypertensive disorders of pregnancy
-Chronic renal disease
-Maternal diabetes
-Antiphospholipid syndrome and related autoimmune disease
-Cyanotic heart disease
COMMON FETAL INDICATIONS:
-Intrauterine growth restriction (IUGR)
-Reduced fetal movement
-Post date pregnancy
-H/o previous IUD , still birth , IUGR , oligohydramnios
-Raised serum alpha protein

4. METHODS OF ANTENATAL FETAL SURVEILLANCE
1) Fetal Movement Counting
2) Non-Stress Test
3) Contraction Stress Test
4) Sonographic Assessment of Fetal Behaviour and/or
5) Amniotic Fluid Volume
6) Arterial and venous doppler
- Uterine Artery Doppler
- Umbilical Artery Doppler
- Other adjuvant Doppler Parameters including
MCA , Ductus venosus , IVC , thoracic aorta ,
Umbilical vein et al

5. DOPPLER ULTRASOUND
Doppler ultrasonography is a non-invasive procedure
that uses detectable changes in high frequency sound waves
(2-20 MHz), based on the Doppler effect, to create clear
digital images in real time.
Doppler ultrasonography is based on two basic principles:
1. Ultrasound principle:
High-frequency sound wave aimed at a stationary target will
be reflected back and detected. The machine then displays
the distances and intensities of the echoes on the screen,
forming a two dimensional image
2. Doppler principle
Echoes from moving target exhibit slight differences in the
time for the signal to be returned to the receiver . It brings
changes in the sound pitch depending on the movement of
the object ( blood) in relation to the detector (positive or
negative shift)- the speed of sound in blood is 1570 m/s)

6. When the frequency of sound
emitted from a stationary
source is fixed, and its
insonation angle is known, the
Doppler shift (i.e. the
difference between the
emitted and the reflecting
frequency) f D = 2f0v cosθ/c
where
f D = Doppler shift,
f0 = frequency of the
transmitted beam,
v = velocity of sound within
the tissue,
θ = insonation angle &
c = speed of sound in tissue
:.
PRINCIPLES OF DOPPLER SHIFT

7. TYPES OF DOPPLER ULTRASOUNDS
1.Continuous wave Doppler ultrasound
Continuous emissions from transducer, enabling the
measurement of high velocity blood flow and
reception of sound. E.g Umbilical Artery signals
returning from the insonated tissues overlap and are
not distinguished as separate entities vessel the
signal is coming from. Not useful for small vessels.
2.Pulsed wave doppler
PW emits pulses of sound only for a fraction of time
and receives the returning signals the rest of the
time. Each returning echo is recognized by its timing
and thus the system defines the depth of the
structure . As it is gray scale, imaging of small and
tortuous vessels is extremely inaccurate.
3.Duplex Doppler ultrasound
Combination of previous two types, in order to
allow accurate anatomical location of studies blood
flow. Good for assessing small and tortuous vessels

8. 4. Color Flow Imaging
Color Doppler Imaging (CDI)
# Here color-coded pulsed Doppler information is superimposed on the B-mode
ultrasonic image.
# Color is assigned to flow direction. Stationary structures are presented in
basic gray-scale image.
#The color saturation is related to the magnitude of the frequency shift .
#Color flow imaging facilitates the detection of small vessels and slow
blood-flow velocity.
#The CDI rely on mean velocity of the blood flow ,so uses impedance
indices (RI/PI) .
Color Doppler Energy (CDE)
#It detects the energy of Doppler signals generated from moving blood.
#CDE is able to display lower volumes and velocities. It enable the
investigation of blood flow with very low velocity, even in the vessels
running at 90 degrees to the insonation angle of the ultrasound beam .
#CDE is not affected by aliasing like CDI
#The conventional semi quantitative analysis based on the use of impedance
indices (RI/PI )is not applicable to CDE studies since it measures the
amplitude of signal.

9. The size of the Doppler signal is dependent on:
(1) Blood velocity: As velocity increases, so does the Doppler
frequency. Increase in viscosity has opposite effect.
(2) Ultrasound frequency: Higher ultrasound frequencies give
increased Doppler frequency. As in B-mode, lower ultrasound
frequencies have better penetration. The choice of frequency is a
compromise between better sensitivity to flow or better
penetration.
(3) The angle of insonation: The Doppler frequency increases
as the Doppler ultrasound beam becomes more aligned to the
flow direction (the angle θ between the beam and the direction
of flow becomes smaller).
(4) Aliasing:
(5) Type of machine used
(6) Expertise of the Ultrasonologist

10. A: Higher-frequency Doppler signal (beam aligned to the direction of )
B: Less aligned than A and produces lower-frequency Doppler signal
C: The beam/flow angle is almost 90°and there is a very poor Doppler signal
D: The flow is away from the beam and there is a negative signal

13. STRUCTURE OF PLACENTA

14. PLACENTA - A UNIQUE ORGAN
The conversion of the spiral arteries to uteroplacental arteries is termed
a physiological change
.
Spiral arteries becomes dilated and tortuous.The diameter increases
from 15–20 to 300–500 mm, due to the invasion of cytotrophoblast cell
which leads to a complete absence of muscular and elastic tissue, no
continuous endothelial lining, mural thrombi and fibrinoid deposition
It reduces the impedance to flow and creates high-flow, low-resistance
placental circulation and optimizing fetomaternal exchange in the
intervillous space. This modification permit the ten-fold increase in
uterine blood flow which is necessary to meet the respiratory and
nutritional requirements of the fetus and placenta
It occur in two stages: the first wave of trophoblastic invasion converts
the decidual segments of the spiral arteries in the first trimester and the
second wave converts the myometrial segments in the second trimester .

15. (1) Resistance index (RI) (also called resistive index or
Pourcelot’s index)
(2) Systolic/diastolic (S/D) ratio, also called the A/B ratio
(3) Pulsatility index (PI)
All are angle independent ratios

16. DOPPLER INDICES
All three indices were found to correlate well with the
actual impedance to flow. :
1. When diastolic flow increases the S/D ratio
decreases.
2. When end diastolic velocity is absent (zero), the
S/D ratio becomes infinite.
3. The lower the diastolic velocity in the S/D ratio the
larger the systematic error.
4. In cases with absent or reverse diastolic flow
velocity only the PI can provide us with a measurable
entity for future reference.

17. UTERINE ARTERY DOPPLER
Uterine artery Doppler provides flow resistance information
on the maternal surface of the placenta( maternal-placental
unit) and therefore reflects the adequacy of trophoblastic
invasion and spiral artery conversion.
In normal pregnancy the S/D ratio or RI values significantly
decrease with advancing gestation until 24 to 26 weeks.

18. UTERINE ARTERY SAMPLING SITE
First-trimester uterine artery evaluation (Figure 1)
1. Transabdominal technique
• Transabdominally, a midsagittal section of the uterus is
obtained and the cervical canal is identified. The probe is
then moved laterally until the paracervical vascular plexus is
seen. Color Doppler is turned on and the uterine artery is
identified as it turns cranially to make its ascent to the
uterine body..
2. Transvaginal technique contd…..

19. Second-trimester uterine artery evaluation
1. Transabdominal technique
• Transabdominally, the probe is placed longitudinally in the
lower lateral quadrant of the abdomen, angled medially. Color
flow mapping is useful to identify the uterine artery as it is
seen crossing the external iliac artery.
• The sample volume is placed 1 cm downstream from this
crossover point.
• In a small proportion of cases if the uterine artery branches
before the intersection of the external iliac artery, the sample
volume should be placed on the artery just before the uterine
artery bifurcation.
• The same process is repeated for the contralateral uterine
artery.
• With advancing gestational age, the uterus usually
undergoes dextrorotation. Thus, the left uterine artery
does not run as lateral as does the right.

20. Normal Pregnancy - Uterine artery waveform
Normal impedance to flow in the
uterine arteries in 1º trimester
Normal impedance to flow in the
uterine arteries in early 2ºtrimester
Normal impedance to flow in the
uterine arteries in late 2º and 3º
trimester

21. ABNORMAL UTERINE A. DOPPLER
Normal impedance to flow in the
uterine arteries (with the
characteristic waveform of early
diastolic notching)
Increased impedance to flow in the
uterine arteries (with the
characteristic waveform of early
diastolic notching)
Very high resistance to flow in the
uterine arteries (with reverse
diastolic flow)
WAVEFORM

22. Predictive value of Uterine A. doppler findings
There is an association between high resistance uterine artery
Doppler at the end of first trimester (11-14 weeks) and in
mid-trimester, with the subsequent development of early-onset
fetal growth restriction, pre-eclampsia and abruption.
This is being used by various centres as screening modality
in High risk cases.
Uterine artery Doppler was considered abnormal between 19
and 23 weeks’ gestation if -
# Resistance index( RI) greater than the 95th centile
# Early diastolic notch in either of the two uterine
arteries)
# When the mean PI of both uterine arteries was
greater than (1.45 – 1.58)

23. UTERINE ARTERY DOPPLER ( RCOG guidelines )
#In a low risk population 2nd trimester has limited accuracy to
predict a SGA.
#In high risk populations Doppler at 20–24 weeks of pregnancy
has a moderate predictive value for a severely SGA neonate.
#In women with an abnormal UA Doppler at 20–24 weeks of
pregnancy, subsequent normalisation of flow velocity indices is
still associated with an increased risk of a SGA neonate.
#Women with an abnormal UA Doppler at 20–24 weeks
(defined as a pulsatility index [PI] > 95th centile) and/or
notching should be referred for serial ultrasound measurement
of fetal size, AFI , BPP with umbilical artery Doppler
commencing at 26–28 weeks of pregnancy.
#Women with a normal uterine artery Doppler should be
offered a single scan for fetal size and umbilical artery Doppler
during the 3rd trimester.

24. UMBILICAL ARTERY DOPPLER
- Umbilical Artery Doppler is essentially placental, rather
than fetal Doppler, providing information on the fetal side
of the placenta.
- Flow velocity measurements performed at this level
represent downstream resistance, namely those at
placental stem and terminal villi

25. UMBILICAL ARTERY SAMPLING
It is easy to sample , Best site is near its origin from the
placenta . Here it gives better representation of downstream
impedence ( i.e Placenta )

26. NORMAL PREGNANCY - UMBILICAL A. WAVEFORM
Normal impedance to flow in the umbilical
arteries and normal pattern of pulsatility at the
umbilical vein in 1º trimester
Normal impedance to flow in the umbilical
arteries and umbilical vein in early 2ºtrimester
Normal impedance to flow in the umbilical
arteries and umbilical vein in late 2º and 3º
trimester

27. CHARACTERISTICS OF UMBILICAL ARTERY
WAVEFORM & INDICES
• The Umb arterial waveform usually has a “Saw
tooth" type pattern with flow always in the forward
direction.
•The S/D ratio decreases, from about 4.0 at 20 weeks to
2.0 at term. The S/D ratio is generally less than 3.0
after 30 weeks
•Umb A. Doppler may be a useful adjunct in the
management of pregnancies complicated by FGR
•No role in screening of low-risk pregnancies or for
complications other than growth restriction

28. PREDICTIVE VALUE OF UMBILICAL A. WAVEFORM
AND INDICES
# If impedance is increased in Umb A > 60% of the
placental vascular bed is obliterated
# AEDF and REDF have an associated 40% and 70%
perinatal mortality, respectively8.
# AEDF in Umb A and MCA PI < 5th percentile are
considered "early" stage changes of IUGR.
# REDF in the Umb A, along with pulsation in Umb
Vein are the best predictor of severe fetal distress, so
termination of pregnancy must be considered as soon
as possible.

29. ABNORMAL UMBILICAL A. DOPPLER WAVEFORM
- High pulsatility index
- Very high pulsatility index
Umbilical arteries (AEDV)
- Very high pulsatility index.
- End diastolic velocity
- Pulsation in the umbilical vein
Umbilical arteries(REDV)
- Severe cases absence of reversal of
end diastolic frequencies

30. ABNORMAL:
•If the S/D ratio is above the 95th percentile for
gestational age.
•In extreme cases of growth restriction, end-diastolic
flow may become absent or even
reversed
•These are ominous findings and should prompt a
complete fetal evaluation—almost half of cases are
due to fetal aneuploidy or a major anomaly
•In the absence of a reversible maternal
complication or a fetal anomaly, reversed end-diastolic
flow suggests severe fetal circulatory
compromise and usually prompts immediate
delivery

31. UMBILICAL ARTERY DOPPLER (RCOG guidelines)
#In a high–risk population, the use of umbilical artery
Doppler has been shown to reduce perinatal morbidity and
mortality. Umbilical artery Doppler should be the primary
surveillance tool in the SGA fetus.
#When umbilical artery Doppler flow indices are normal it is
reasonable to repeat surveillance every 14 days.
#More frequent Doppler surveillance may be appropriate in a
severely SGA infant.
#When umbilical artery Doppler flow indices are abnormal
(pulsatility or resistance index > +2 SDs above mean for
gestational age) and delivery is not indicated repeat
surveillance twice weekly in fetuses with end–diastolic
velocities present and daily in fetuses with absent/reversed
end–diastolic frequencies.

32. MIDDLE CEREBRAL ARTERY DOPPLER
The middle cerebral artery is the most studied
cerebral artery because
(a) it is easy to sample
(b) it provides information on the cerebral blood
flow in normal and IUGR fetuses and
(c) it can be sampled at an angle of 0° between
the ultrasound beam and the direction of the blood
flow.
Therefore, for the middle cerebral artery we are able
to determine angle-independent indices (the most
used is the pulsatility index) and also the real
velocity of blood flow.

33. MIDDLE CEREBRAL ARTERY SAMPLING

34. What is the appropriate technique for obtaining fetal
middle cerebral artery Doppler waveforms?
• An axial section of the brain, including the thalami and the
sphenoid bone wings, should be obtained and magnified.
• Color flow mapping should be used to identify the circle
of Willis and the proximal MCA.
• The pulsed-wave Doppler gate should then be placed at
the proximal third of the MCA, close to its origin in the
internal carotid artery10 (the systolic velocity decreases
with distance from the point of origin of this vessel).
• The angle between the ultrasound beam and the direction
of blood flow should be kept as close as possible to 0◦ • At
least three and fewer than 10 consecutive waveforms should be
recorded. The highest point of the waveform is considered as
the PSV (cm/s).

35. MIDDLE CEREBRAL ARTERY WAVEFORM
Color Doppler examination of the circle of Willis (left). Flow velocity
waveforms from the middle cerebral artery in a normal fetus with low
diastolic velocities (right, top) and in a growth-restricted fetus with
high diastolic velocities (right, bottom)

36. Fetal middle cerebral arterial (MCA) Doppler
assessment is an important part of assessing
a) Fetal cardiovascular distress
b) Fetal anemia ( Peak Systolic Flow Velocity)
c) Fetal hypoxia ( brain sparing effect)
It is a very useful adjunct to Umbilical Artery
doppler asessment in IUGR fetus.
#A normal fetal MCA S:D ratio should always
be higher than the Umbilical arterial S:D ratio.
# Measurement of the fetal MCA (PSFV) is a
predictor of severe fetal anemia and can be used to
avoid unnecessary invasive procedures in red
blood cell isoimmunized pregnancies.

37. INTERPRETATION
# In the normal situation the fetal MCA has a high
resistance flow which means there is minimal
antegrade flow in fetal diastole.
# In pathological states this can turn into a low
resistance flow ( reduced PI) mainly as a result of
the FETAL HEAD SPARING EFFECT.
# Paradoxically in some situations such as with
severe cerebral oedema and due to acidemia , the
flow can revert back to a high resistance pattern
when the pathology hasn't yet resolved which is
again an ominous sign and call for termination of
pregnancy.

38. DUCTUS VENOSUS DOPPLER
Ductus venosus (DV) flow Doppler is a useful
parameter since of all the pre-cardial veins, the
Ductus venosus allows the most accurate
interpretation of fetal cardiac function as well as
myocardial haemodynamics
# First trimester screening : Aneuploidic anomalies
# Second trimester scanning: It is useful in assessing-a)
Severity of hypoxemia in IUGR
b) Myocardial compromise

39. DUCTUS VENOSUS SAMPLING

40. What is the appropriate technique for obtaining fetal
venous Doppler waveforms?
Ductus venosus
• The ductus venosus (DV) connects the intra-abdominal
portion of the umbilical vein to the left portion of the inferior
vena cava just below the diaphragm. The vessel is identified
by visualizing this connection by 2D imaging either in a
midsagittal longitudinal plane of the Fetal trunk or in an
oblique transverse plane through the upper abdomen.
• Color flow mapping demonstrating the high velocity
at the narrow entrance of the DV confirms its identification
and indicates the standard sampling site for Doppler
measurements.
• Doppler measurement is best achieved in the sagittal
plane from the anterior lower fetal abdomen since alignment
with the isthmus can be well controlled.

41. DUCTUS VENOSUS NORMAL DOPPLER WAVEFORM
This triphasic waveform comprises of
S wave : corresponds to fetal ventricular systolic contraction and is the
highest peak
D wave : corresponds to fetal early ventricular diastole and is the second
highest peak
A wave : corresponds to fetal atrial contraction and is the lowest point in the
wave form albeit still being in the forward direction

42. Normal ductus venosus waveform at 12 weeks of
gestation with positive flow during atrial
contraction.

43. Ductus venosus flow velocity waveform with low
but positive forward flow during atrial contraction.

44. Ductus venosus reverse ‘a’ waveform

45. ABNORMAL DUCTUS VENOSUS WAVEFORM
1) Aneuploidic anomalies
Down syndrome : ~ 80% are thought to have
abnormal waveform
2)Congenital cardiac anamolies
3)Fetal pulmonary arterial anomalies e.g atresia
4) Fetal tumors like sacrococcygeal teratoma
5)Twin to twin transfusion syndrome
6) Maternal Diabetes: may exhibit increased PI
values
Growth restricted fetuses with abnormal Ductus
venous flow have worse perinatal outcome
compared to those where flow abnormality is
confined to the umbilical or middle cerebral artery

47. Typical progression of multi-vessel Doppler studies with
progressive placental dysfunction-
-Elevated umbilical artery S/D ratio
-Middle cerebral artery PI < 5th percentile (brain-sparing)
-Umbilical artery - absent diastolic flow
-Umbilical artery - reversed diastolic flow
-Ductus venosus - elevated pulsatility index
-Ductus venosus - reversed a-wave
-Ductus venosus - decreased IVR, reversed a-wave
-Umbilical vein double pulsations
-Umbilical vein triple pulsation with reversed a-wave
flow

48. Progressive deterioration in fetal cardiovascular and behavioural
variables seen with declining metabolic status.

51. TAKE HOME MESSAGE
#Doppler ultrasound provides a non-invasive
method for the study of fetal hemodynamics.
#Investigation of the uterine and umbilical arteries
gives information on the perfusion of the
uteroplacental and fetoplacental circulations, resp
#Doppler studies of selected fetal organs are valuable
in detecting the hemodynamic rearrangements that
occur in response to fetal hypoxemia.
contd…

52. #Doppler velocimetry gives the most important
information to differentiate the truly growth-restricted
fetus (IUGR) from the fetus that is
constitutionally small but otherwise normal in
cases where AFV is normal .
#It act as screening as well as diagnostic modality
in high risk cases and can guide regarding
frequency of follow up & timely intervention.
#Ductus venosus doppler done in the first
trimester is a part of screening tools for detecting
aneuploidy.
contd….

53. #First trimester uterine artery PI value in high risk
cases is being used as a screening tool in few centres
to detect preeclampsia cases early .
# Presence of single umbilical artery is not only an
indicator of aneuploidy but it also predicts IUGR in
10% cases and calls for suveillance.
#Middle cerebral artery PSFV value has taken over
Delta OD 450 in assessing the severity of fetal
anemia in Rh alloimmunised fetuses. It is also used
to manage such cases by interpreting the rise in Hb
in cases of intruterine blood tranfusions and helps
in deciding further need as well.
………………………………

54. UTERINE ARTERY
9WKS
19 WKS
19 WKS

55. UMBILICAL ARTERY NORMAL WAVEFORM
33WKS|
39 WKS
39WKS

56. DUCTUS VENOSUS NORMAL WAVEFORM
33WKS
13 WKS

57. MIDDLE CEREBRAL ARTERY NORMAL WAVEFORM
33 WKS