Rh incompatibility occurs when a pregnant woman has Rh-negative blood and her fetus has Rh-positive blood inherited from the father. This difference can lead to the mother's immune system producing antibodies against the fetus's red blood cells, which can cause serious health issues for the baby, such as hemolytic disease of the newborn. To prevent complications, doctors often give Rh immunoglobulin (RhIg) to Rh-negative mothers during pregnancy and after delivery. This treatment helps prevent the mother's immune system from reacting to Rh-positive blood cells, reducing the risk of complications in current and future pregnancies.