What causes erythroblastosis fetalis?
• Erythroblastosis fetalis is caused by the red blood cells (RBCs) made by mother and baby being different. There are many ways the RBCs may be different. Incompatible differences are ones that can cause the mother’s body to make antibodies against the baby’s RBCs. This happens when you have been pregnant before and your immune system was exposed to that baby’s blood. Your exposure to that baby’s blood may have happened during pregnancy, miscarriage, abortion, or delivery. This past exposure makes your immune system sensitive to the presence of foreign blood. The next time you get pregnant, your body reacts more strongly and makes many more antibodies. • The RBC incompatibilities that usually cause erythroblastosis fetalis are called Rh factor and ABO. Rh factor incompatibility happens when you are Rh negative (Rh-) and your baby is Rh positive (Rh+). ABO incompatibility may happen if you and your baby have different major blood types. A, B, and O are the three major blood types. ABO i
