When you begin prenatal care, your midwife will obtain blood samples to screen for a variety of diseases and blood factors. One of these factors is the Rhesus antibody (Rh factor). It is part of what we call your “blood type”. If your blood contains the Rh(D) antigen, then your blood type is Rh positive. If it does not contain the Rh(D) antigen, then your blood type is Rh negative.
Women whose Rh factor is negative have special considerations in pregnancy. We will need to test the father’s blood. If the father of your baby is Rh negative, then you will have an Rh negative baby and there is nothing you need to do. If the father of your baby is Rh positive, there is a chance you will have an Rh positive baby. (If we can’t test the father’s blood, we will assume he is Rh positive.)
When Rh negative women are pregnant with an Rh positive baby, there is a slight chance that baby’s blood may come in contact with the mother’s blood. If that happens, the mother will begin to produce antibodies against the Rh positive blood. We call this isoimmunization or sensitization. Sensitization is not usually a problem for the pregnancy in which it occurs, but it can cause a problem with subsequent pregnancies.
Hemolytic Disease of the Newborn (HDN), also called erythroblastosis fetalis, is caused by Rh(D) isoimmunization. The antibodies that an Rh negative mother produces when she has previously come into contact with Rh positive blood can cause destruction of the fetal red blood cells, causing severe anemia, cardiac problems, and possibly death depending on the severity of the mother’s reaction.
HDN can be prevented by administering RhoGAM to a mother during pregnancy- usually at 28 weeks- and again after birth (within 72 hours). RhoGAM is administered by intramuscular injection. RhoGAM initiates a passive immune response that will prevent sensitization to the Rh positive antigen.
RhoGAM [Rh(D)-immune globulin] is a blood product. There is a possibility that blood-borne pathogens and DNA can be transmitted with the injection.
RhoGAM decreases the incidence of fetal death from hemolytic disease- from about 1% to 0.00004%.
Rh negative women should have an antibody screen at the beginning of pregnancy and at 28 weeks.
Babies born to Rh negative mothers will have their cord blood tested for type and Rh factor. When baby is Rh positive, the mother will receive another RhoGAM injection within 72 hours of birth.