Generic Name Brand Name Rh immune globulin HypRho-D, MICRhoGAM, RhoGAM
Rh immune globulin contains antibodies to the Rh factor in blood. The antibodies come from donors who have become sensitized to the Rh factor. Giving these Rh antibodies to an Rh-negative pregnant woman prevents her immune system from producing its own Rh antibodies, which would attack her Rh-positive fetus's red blood cells.
When introduced into an Rh-negative mother's bloodstream, Rh immune globulin antibodies locate any Rh-positive fetal red blood cells that are present. The antibodies attach to the Rh-positive red blood cells, masking their presence from the mother's immune system. Although the Rh immune globulin antibodies destroy fetal red blood cells, not enough are destroyed to harm the fetus.
Rh immune globulin is given by injection into a muscle (intramuscular, or IM).
Rh immune globulin is given to all Rh-negative women who may be carrying an Rh-positive fetus. While it prevents Rh sensitization, Rh immune globulin cannot prevent damage to an Rh-positive fetus if the mother is already sensitized to the Rh factor.
Rh immune globulin should be given to an Rh-negative woman to prevent sensitization:1
- After amniocentesis, fetal blood sampling, or chorionic villus sampling.
- When bleeding occurs in the second or third trimester of pregnancy.
- At 28 weeks of pregnancy.
- After an external cephalic version of a breech fetus.
- After abdominal trauma during pregnancy.
- Within 72 hours after delivery of an Rh-positive infant.
- After a threatened or complete miscarriage, or an induced abortion.
- Before or immediately after treatment for ectopic pregnancy or a partial molar pregnancy.
Rh immune globulin is highly successful at preventing sensitization in a current pregnancy. When given at 28 weeks and within 72 hours of delivery of an Rh-positive child, it has a success rate of greater than 99%.1
Side effects from Rh immune globulin are extremely rare and include:
- Discomfort at the site of injection.
- Slight fever.
- An allergic reaction to tiny amounts of proteins in the injection.
Rh immune globulin does not carry a risk of human immunodeficiency virus (HIV) or other types of infections.
See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)
Although Rh immune globulin is not given to a woman who has become sensitized to the Rh factor, it is not harmful to a sensitized woman.
The dosage of Rh immune globulin can be adjusted to protect against exposure to varying amounts of Rh-positive blood. Exposure to large amounts of Rh-positive blood—caused by an injury, accidental transfusion with Rh-positive blood, or complication during labor and delivery—will require a higher dose of Rh immune globulin. A smaller-than-average dose may be given after an ectopic pregnancy, molar pregnancy, induced abortion, or miscarriage (spontaneous abortion) in early pregnancy.
If given within 3 months of a live virus immunization, Rh immune globulin may block the benefit of the immunization. Your doctor will be able to tell you whether you need another immunization.
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American College of Obstetricians and Gynecologists (1999, reaffirmed 2010). Prevention of Rh D alloimmunization. ACOG Practice Bulletin No. 4. Obstetrics and Gynecology, 93(5): 1–7.
By Healthwise Staff Primary Medical Reviewer Sarah Marshall, MD - Family Medicine Specialist Medical Reviewer William Gilbert, MD - Maternal and Fetal Medicine Last Revised October 20, 2011