Rh immune globulin

Examples

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Brand Name	Chemical Name
RhoGAM	Rh immune globulin

How It Works

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Rh immune globulin contains antibodies to the Rh factor in blood. The antibodies are obtained 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).

Why It Is Used

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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 if an unsensitized woman is carrying an Rh-positive fetus or if her fetus's blood type is unknown and the father is Rh-positive.
• 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.

How Well It Works

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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

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Side effects from Rh immune globulin are extremely rare and include:

• Discomfort at the site of injection.
• Slight fever.
• An allergic reaction to trace amounts of proteins in the injection.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

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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, or miscarriage (spontaneous abortion) in early pregnancy.

Rh immune globulin should not be given within 2 months of an immunization, because it will block the benefit of the immunization.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.

References

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Citations

1. American College of Obstetricians and Gynecologists (1999). Prevention of Rh D alloimmunization. ACOG Practice Bulletin No. 4. Obstetrics and Gynecology, 93(5): 1–7.

Credits

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Author	Kathe Gallagher, MSW
Editor	Kathleen M. Ariss, MS
Associate Editor	Lisa Shaw
Primary Medical Reviewer	Patrice Burgess, MD - Family Medicine
Specialist Medical Reviewer	Gregory A L Davies, MD, FRCSC, FACOG - Maternal-Fetal Medicine
Specialist Medical Reviewer	Kirtly Jones, MD - Obstetrics and Gynecology
Last Updated	November 10, 2005