Final answer:
Rh incompatibility issues occur when an Rh-negative individual is sensitized to Rh-positive cells, usually during a first pregnancy, and subsequently carries another Rh-positive fetus, leading to hemolytic disease of the newborn in later pregnancies.
Step-by-step explanation:
Problems associated with Rh incompatibility are most likely to arise when an Rh-negative individual has been exposed to Rh-positive red blood cells, leading to sensitization and the subsequent production of anti-Rh antibodies. This exposure typically occurs during or after the first pregnancy with an Rh-positive fetus. If the Rh-negative individual carries another Rh-positive fetus, the previously formed anti-Rh antibodies can cross the placenta and lead to hemolysis of the fetal red blood cells, a condition known as hemolytic disease of the newborn (HDN) or erythroblastosis fetalis. HDN can result in anemia or more severe consequences such as fetal death if untreated. The risk of HDN increases in second or subsequent pregnancies with an Rh-positive fetus.