Final answer:
A person with Rh- blood may develop anti-Rh agglutinins if exposed to Rh+ blood through transfusion or pregnancy with an Rh+ baby. Sensitization and a subsequent exposure can cause hemolytic disease of the newborn, but this condition is preventable with RhoGAM injections.
Step-by-step explanation:
A person with Rh-negative (Rh-) blood may develop anti-Rh agglutinins, or antibodies, under certain conditions. This process is known as sensitization. It occurs when a person with Rh- blood is exposed to Rh-positive (Rh+) blood, which can happen through a blood transfusion with Rh-incompatible blood or during pregnancy when an Rh- woman gives birth to an Rh+ baby. The first exposure to Rh+ blood cells typically does not cause a reaction; however, the immune system starts to generate anti-Rh antibodies. Upon a second exposure to Rh+ blood, such as during a subsequent pregnancy with an Rh+ fetus, these antibodies can cross the placenta, resulting in agglutination and hemolysis of the fetal red blood cells, a condition known as hemolytic disease of the newborn (HDN) or erythroblastosis fetalis. This can be severe and life-threatening to the fetus but can be prevented with the injection of RhoGAM during and after the first pregnancy.