Management of Rh-Sensitized Pregnant Patient
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Transcript of Management of Rh-Sensitized Pregnant Patient
Management of
Rh-Sensitized Pregnant Patient Prof. Aboubakr Elnashar Benha University Hospital. Egypt
Aboubakr Elnashar
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
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
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,
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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).
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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
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Fetal blood sampling (Hct<30%):
<35 w: intrauterine transfusion
>35 w: delivery
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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
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Frequency
•Initiated: as early as 18 w
•Repeated: every 1–2 w as the clinical situation
warrants.
Aboubakr Elnashar
Aboubakr Elnashar
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.
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Power Doppler with visualization of the Circle of Willis and the Middle cerebral artery.
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Normal flow of the MCA in 1- st trimester
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Normal flow of the MCA in 2 and 3 trimester.
Flow velocity wave form in the fetal MCA in a normal fetus at 22w Aboubakr Elnashar
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
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
The solid curve indicates the median MCA-PSV The dotted curve indicates 1.5 multiples of the median.
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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
Aboubakr Elnashar
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
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
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
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
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.
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Flow velocity waveform in the fetal MCA in a severely anemic fetus at 22 w. blood velocity is increased
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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.
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6. Serial NSTs or BPPs Weekly beginning at 32 W.
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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
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
Thank you
Aboubakr Elnashar