Rh- Incompatibility (Fact sheet #6)
People with different blood types have proteins specific to that blood type on the surfaces of their red blood cells (RBCs). There are four blood types — A, B, AB, and O. Each of the four blood types is further classified based on the presence of another protein on the surface of RBCs that indicates the Rh factor. If you carry this protein, you are Rh positive. If you don't carry the protein, you are Rh negative. Most people — about 85% — are Rh positive. But if a woman who is Rh negative and a man who is Rh positive conceive a baby, there is the potential for a baby to have a health problem. The baby growing inside the Rh-negative mother may have Rh-positive blood, inherited from the father. Approximately half of the children born to an Rh-negative mother and Rh-positive father will be Rh positive. During delivery, the mother's and baby's blood can intermingle. If this happens, the mother's body recognizes the Rh protein as a foreign substance and might begin maki...