Final answer:
The immune system of an Rh-negative mother may create anti-Rh antibodies during or after her first pregnancy, potentially causing hemolytic disease of the newborn in subsequent pregnancies with Rh-positive babies if not treated with anti-Rh immune globulin.
Step-by-step explanation:
When an Rh-negative mother becomes pregnant with an Rh-positive fetus, the mother's immune system may generate anti-Rh antibodies if the fetal blood cells enter her bloodstream. This situation usually does not affect the first pregnancy because the sensitization often occurs too late to harm the first child. However, during subsequent pregnancies, if there's another Rh-positive fetus, the anti-Rh antibodies that the mother produced earlier can cross the placenta and lead to hemolytic disease of the newborn (HDN), also known as erythroblastosis fetalis. HDN can result in fetal anemia or more severe complications if it is not treated. To prevent this, Rh-negative mothers are given anti-Rh immune globulin during and after their first pregnancy to destroy any fetal Rh-positive cells that might cause them to form anti-Rh antibodies.