Final answer:
Erythroblastosis fetalis is caused by an Rh- mother previously sensitized by pregnancy with an Rh+ child becoming pregnant with another Rh+ child. Anti-Rh antibodies produced by the mother can attack the blood of the fetus and lead to anemia. The disease can be prevented by administering anti-Rh antibodies to the mother during her first pregnancy.
Step-by-step explanation:
Erythroblastosis fetalis, also known as hemolytic disease of the newborn, is caused by an Rh- mother previously sensitized by pregnancy with an Rh+ child becoming pregnant with another Rh+ child. During the mother's first pregnancy, fetal blood enters her circulatory system, and anti-Rh antibodies are made. These antibodies can then cross the placenta and attack the blood of the Rh+ fetus during subsequent pregnancies, leading to anemia and potentially severe complications. To prevent this, the mother can receive anti-Rh antibodies (RhoGAM) during her first pregnancy to destroy Rh-positive fetal red blood cells and prevent the antibody response.