Final answer:
Rh antibodies are produced by Rh- individuals only after exposure to Rh+ blood. Without preventive treatment with RhoGAM during pregnancy, an Rh-mother may produce antibodies that can lead to erythroblastosis fetalis in subsequent Rh+ pregnancies.
Step-by-step explanation:
Rh Factor and Erythroblastosis Fetalis:
Unlike ABO blood group antibodies that are preformed, antibodies to Rh antigen are not naturally present in Rh-negative (Rh-) individuals. They are produced upon exposure to Rh-positive (Rh+) blood, a process known as sensitization. Approximately 85% of Americans are Rh+. If an Rh-mother carries an Rh+ fetus, she may become sensitized during childbirth when fetal blood cells enter her bloodstream, leading to the production of anti-Rh antibodies. During a subsequent pregnancy with an Rh+ fetus, these antibodies can cross the placenta, potentially causing erythroblastosis fetalis.
To prevent this, a Rh-mother is given a preventive treatment called RhoGAM to avoid the immune response that leads to the disease. This occurs when a Rh-mother carries multiple Rh+ fetuses and develops anti-Rh antibodies after exposure to the Rh antigen. If the mother does not receive preventative treatment, the antibodies can cross the placenta and destroy the red blood cells of subsequent Rh+ fetuses, causing severe complications.