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IsoimmunizationErythroblastosis Fetalis
Hemolytic Disease of the Newborn
Zeev Weiner
Director of Ultrasound in Obstetrics and Gynecology
Lutheran Medical Center
Rh Isoimmunization
Rh Blood Group System:
Cc
Dd
Ee
40 other antigens: Du, Cw,….
The D antigen
In 85% the D antigen is present
55% heterozygous
Sensitization occurs during blood transfusion and during pregnancy
The D antigen
Isoimmunization is dose dependent
0.1 ml is sufficient
ABO incompatibility confers partial protection!
Obstetrical risks for Rh isoimmunization
Abortions (2-5%) – How early?
Pregnancy and delivery (1.6%)
Procedures: Amniocentesis
Trauma
Rh Hemolytic Disease
Mild: Fetal anemia with Hb>12-13g/dl.
No sonographic findings.
Rh Hemolytic Disease
Moderate: Fetal anemia with Hb between 7-12 g/dl
Possible sonographic findings.
Rh Hemolytic Disease
Severe: Anemia with Hb < 7g/dl
Most of the time there are sonographic findings
Monitoring the sensitization
When do we check anti-D titers? At the beginning, 28 wks, after birth
What is a significant titer?Above 1:8-1:16
How accurate are the titers?……..
What is the meaning of very low titers and do we have to give prophylaxis?
…….
Follow-up patients with sensitization
Checking the Rh antigens of the father if negative no need to
follow-up?
Checking the Rh antigens of the fetus if negative definitely no need to
follow-up
Follow-up patients with Rh isoimmunization
Follow-up can start at 18 weeks gestation
There are 3 options:
Amniocentesis
Cordocentesis
Doppler
Amniocentesis for patients with Rh isoimmunization
The Liley or the modified curves.
Advantage: less complicated procedure
Disadvantage: delta OD may not accurately correlate with the anemia
Cordocentesis for patients with Rh isoimmunization
Blood sampling from the umbilical vein, hepatic or portal veins,
intracardiac
Advantage: more reliable, immediate option for treatment
Disadvantage: higher risk
Doppler studies for patients with Rh isoimmunization
Peak velocity of the middle cerebral artery (why not other vessels?)
Advantage: non invasive
Disadvantage: correlation with anemia is still questionable
Treatment of Fetal Anemia
Indication: Hb < 10-11 g/L (Hct<30) or fetal hydrops
Technique: Intraperitoneal, Intravascular (umbilical vein or
others), Intracardiac
Treatment of Fetal Anemia
Irradiated O- packed red cells (Hct=0.85-0.9)
V =[(Hct-f - Hct-i)xEFWx120]: Hct-d
Guidelines for repeat transfusion: 1% decline per day, Hct=25
Treatment of Severe Cases of Rh Isoimmunization
Early transfusions starting at 16-18 wks
A weekly high-dose of IVIG between 13-18 wks
AID
Time and Mode of Delivery
33-34 wks with documented lung maturity
34-36 weeks with no need to document lung maturity
No indication for a CS
Prevention of Rh Isoimmunization
300 micrograms of Anti-D Ab
At 28 wks and within 72 hrs postpartum
Protect against 15 ml of RBC
Other Common antibodies Causing Isoimmunization
Kell
C
E