Erythroblastosis fetalis, hemolytic disease of the newborn, is extremely rare today because physicians carefully track Rh status. An Rh-negative woman who might carry an Rh-positive fetus is given an injection of a drug called RhoGAM. This injection is actually composed of anti-Rh antibodies, which bind to and shield any Rhpositive fetal cells that might contact the woman’s cells, sensitizing her immune system. RhoGAM must be given within 72 hours of possible contact with Rh-positive cells, including giving birth, terminating a pregnancy, miscarrying, or undergoing amniocentesis.