Management of Rh-Sensitized Pregnant Patient

1. Management of
Rh-Sensitized Pregnant Patient
Prof. Aboubakr Elnashar
Benha University Hospital. Egypt
Aboubakr Elnashar

2. Any Rh- patient with an anti-D titer >1:4 should
be considered sensitized.
1. Sonogram.
At 1st visit
Accurate dating for G age
{interpret fetal tests
timing of fetal interventions}.
Aboubakr Elnashar

3. 2. Establish Paternal Blood Type.
{The pregnancy is at risk only if the fetus has inherited
the D antigen}.
Paternal Ag: {avoid multiple fetal interventions}.
Paternal red cell phenotype
•If Rh-: the fetus will be Rh- and not at risk: No further
intervention.
•If heterozygous for D: the fetus has a 50% chance of
being at risk.
•If homozygous: the fetus will be at risk for hydrops.
All fetuses must be assumed to be Rh+ until proven
otherwise.
Aboubakr Elnashar

4. 3. Follow Serial Maternal D Antibody
Titer.
Critical titer:
The titer at which fetus is at risk
1:16 or
An increase of >1 dilution (e.g. 1:2 to 1:8).
Once the maternal antibodies surpass the critical titer:
further titers will no longer be helpful
serial fetal testing will be required throughout the remainder of
the pregnancy.
Correlation between titer and severity of disease: poor.
But: significant hemolytic disease
Elevated antibody titers at the beginning of pregnancy
rapid rise in titer
titer of 1 : 64 or greater,
Aboubakr Elnashar

5. 4. Serial Fetal Assessment.
Aim: Determine timing of intervention.
a. Amniocentesis.
Serial beginning at 24 to 26 w {determine the
likelihood of fetal anemia}.
Amniotic bilirubin 2ndry to fetal hemolysis
was directly proportional to the
spectrophotometric peak at 450 nm (OD450)
(Liley, 1961).
Aboubakr Elnashar

6. Zone 1:
The fetus is unlikely to be affected at this time, or only
mildly affected: repeat amniocentesis in 10 to 14 days.
Zone 2:
The fetus is experiencing mild-to-moderate hemolysis.
lower zone (>80%): amniocentesis in 10 to 14 days
upper zone(<80%): fetal blood sampling
Zone 3:
The fetus is anemic. A high probability of fetal death is
present in 7 to 10 days unless intervention occurs: fetal
blood sampling
Aboubakr Elnashar

7. Fetal blood sampling (Hct<30%):
<35 w: intrauterine transfusion
>35 w: delivery
Aboubakr Elnashar

8. b. Middle cerebral artery peak systolic velocity (MCA-
PSV)
The most significant breakthrough in the surveillance of
the potentially anemic fetus
Based on:
In fetal anemia:
Enhanced fetal cardiac output and
Decrease in blood viscosity:
Increased blood flow velocity
preferentially shunt blood to brain faster
most pronounced MCA PSV
Aboubakr Elnashar

9. Frequency
•Initiated: as early as 18 w
•Repeated: every 1–2 w as the clinical situation
warrants.
Aboubakr Elnashar

10. Aboubakr Elnashar

11. Steps:
A transverse view of the fetal brain is obtained at the
level of BPD. The transducer is then moved caudally to
demonstrate the thalamus clearly.
With color flow imaging MCA can be identified as the
major anterolateral branch of the Circle of Willis.
The pulsed Doppler sample gate should be placed at
the junction of the medial third and middle third of this
artery
Pulsed Doppler is then used to measure MCA-PCV just
distal to its bifurcation from the internal carotid artery.
The angle of insonation is invariably small due to the usual occipitotransverse
position of the fetal head.
Since the MCA-PSV is a measurement of absolute instead of relative velocity,
the angle of the fetal Doppler insonation should be kept as close as possible to
0˚ for accurate estimate of the absolute peak systolic flow velocity.
Aboubakr Elnashar

12.  Power
Doppler with
visualization
of the Circle
ofWillis and
the Middle
cerebral
artery.
Aboubakr Elnashar

13.  Normal flow of
the MCA in 1- st
trimester
Aboubakr Elnashar

14.  Normal flow
of the MCA in
2 and 3
trimester.
Flow velocity wave
form in the fetal
MCA
in a normal fetus
Aboubakr Elnashar

15. Top. Color Doppler waveform obtained from the middle
cerebral artery in a normally grown fetus at 34 weeks.
Bottom. Measurements are obtained using the maximum
frequency follower. Aboubakr Elnashar

16. Interpretation
{MCA velocity increase with advancing gestational
age} results are reported in MoM.
The actual value can be plotted on standard curves or
entered into a website that will calculate the MoM value
(www.perinatology.com).
A value greater than 1.5 MoM: moderate to severe f
anemia: further investigation through direct ultrasound-
guided fetal blood sampling (cordocentesis)
After 35 w: false positive rate for the prediction of f
anemia is increased {fetal heart rate accelerations}
Aboubakr Elnashar

17. The solid curve indicates the median MCA-PSV
The dotted curve indicates 1.5 multiples of the median.
Aboubakr Elnashar

18. MCA-PSV plotted as a function of gestational age.
Above the upper line (1.5 multiples of the median): invasive testing and
treatment are indicated.
Below that line, individual monitoring regimes are established.
Aboubakr Elnashar

19. Aboubakr Elnashar

20. Top: Color Doppler waveform of the MCA.
Bottom:The maximum frequency follower has been used
to calculate the PSV (87.9cm).The value lies above the
95th centile for gestation, making it highly suggestive of
fetal anemia. Aboubakr Elnashar

21. MCA waveforms in an anemic
fetus requiring serial
transfusions for severe Rh (D)
disease.
The peak systolic velocities of
62, 50, and 61 cm per second
(top to bottom) corresponded
to fetal hematocrits of 19%,
44%, and 32%, before, at the
time of, and a week after the
first intravascular transfusion,
respectively.
Aboubakr Elnashar

22. Advantage
More sensitive for predicting f anemia than the ΔOD450
(Recent studies)
Alternative to serial amniocenteses
Excellent noninvasive tool for the monitoring of f
anemia.
Reduction of over 80% in the need for invasive
diagnostic procedures such as amniocentesis and
cordocentesis.
Aboubakr Elnashar

23. An accurate predictor of severe f anemia (II-1A)
(Recent systematic review)
Correlation with the fetal hemoglobin value becomes
more accurate as the severity of anemia increases
The correlation between hemoglobin concentration and
the MCA-PSV has rendered amniocentesis for the
measurement of the ΔOD450 an outdated tool
{transfusion therapy should never be initiated without
confirming fetal anemia}.
Aboubakr Elnashar

24. Limitations
1. Reliability decreases after 35 w, so alternative
methods must be used.
2. Dopplers can easily be measured incorrectly: should
be performed only by experienced clinicians.
Aboubakr Elnashar

25. Flow velocity
waveform in the
fetal MCA in a
severely anemic
fetus at 22 w. blood
velocity is increased
Aboubakr Elnashar

26. Other sonographic findings
have been claimed to either precede the development of
hydrops or predict fetal anemia:
amniotic fluid volume
liver and spleen length or thickness
placental thickness
increased bowel echogenicity
cardiac biventricular diameter
none of these are reliable.
Aboubakr Elnashar

27. 6. Serial NSTs or BPPs
Weekly beginning at 32 W.
Aboubakr Elnashar

28. 6. Delivery.
At 35 weeks:
1. Fetus has required transfusion
2. Abnormal Doppler studies
At 37 and 39 weeks:
If the maternal critical titers were not
reached
Aboubakr Elnashar

29. Management of Sensitized Rh-Negative Women
Serial indirect Coombs tests are performed at monthly
intervals after 18 w until the critical titer is exceeded.
• At that time, serial MCA-PSV are performed weekly.
• Cordocentesis is performed when MCA-PSV>1.5 MoM
During the first sensitized pregnancy, the Coombs titer
correlates with the severity of fetal disease. However,
these titers are poorly predictive after the first sensitized
pregnancy.
Aboubakr Elnashar

30. Thank you
Aboubakr Elnashar