Rh-negative blood consists of red blood cells lacking the Rh factor, a surface protein obtained through genetic inheritance, according to the American Congress of Obstetricians and Gynecologists. Rh incompatibility occurs when a pregnant mother is Rh-negative and the fetus is Rh-positive, potentially leading to medical complications.
If Rh-positive blood from the fetus mixes with Rh-negative blood from the mother, the mother's body becomes Rh sensitized and produces antibodies to combat the Rh-positive cells, according to the University of Rochester Medical Center. As antibodies destroy the fetus' red blood cells, anemia develops in the fetus and can lead to illness, brain damage and possibly death, as reported by the American Pregnancy Association.
Complications may be prevented by performing a blood test and antibody screen early in pregnancy. If the Rh-negative mother has not yet developed antibodies to her Rh-positive fetus, then Rh immunoglobulin may be administered to prevent sensitization, as reported by the American Congress of Obstetricians and Gynecologists. If the Rh-negative mother has developed antibodies, the condition of the fetus is closely monitored to prevent possible harm, according to WebMD. In mild or moderate cases, the fetus may be delivered early. In severe cases, the fetus may receive a blood transfusion prior to birth.