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MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Antibody Screen Positive: Rh Disease and Other Atypical Antibodies
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3. Rh Disease and Other Atypical Antibodies
Step 3. How does rhesus innume globulin work?
Rhesus immune globulin (RhIg) is protective most likely by functioning as a blocking antibody, covering antigenic sites on fetal cells that find their way into the maternal blood stream that would otherwise have provoked the maternal anamnestic response. ( Anderson)
RhIg is derived from the plasma of male donors that have been undergone sensitization by repeated injections of RhD-positive red cells. It is purified by ultrafiltration and cold ethanol fractionation and is viral free, and does not contain mercury-based preservatives. It is indicated for prophylaxis in all unsensitized Rh negative women delivering an Rh positive infant, and is also given at 28 weeks to prevent the <1% of cases that occur in the third trimester prior to placental separation. (Bowman)
RhIg is also indicated for induced and spontaneous abortion, ectopic and molar pregnancy, and invasive procedures (chorionic villus sampling and amniocentesis), as well as external cephalic version. In the case of massive feto-maternal hemorrhage (e.g., abruption, major trauma), more than one dose (300 mcg) of RhIg may be indicated. The Kleihauer-Betke test for the presence of fetal cells in the maternal circulation is a labor-intensive and not terribly accurate test, but may be used to help guide the need for additional doses of RhIg in these situations. RhIg is ideally given within 72 hours of the sensitizing event, but should be given up to 2 weeks afterwards if doubt occurs or the opportunity was missed. “If in doubt, give”, but remember, it will be of no benefit to already sensitized women.
