What immune response is triggered when an Rh- mother is sensitized to Rh+ blood?

• A. Allergic response
• B. Autoimmune response
• C. Hemolytic disease of the newborn
• D. Inflammatory response

Answer: (C)

When an Rh-negative (Rh-) mother is sensitized to Rh-positive (Rh+) blood, it can lead to a specific immune reaction known as hemolytic disease of the newborn (HDN). This scenario typically occurs during pregnancy, particularly if the mother is carrying an Rh+ fetus.

During the first pregnancy, if fetal Rh+ red blood cells enter the maternal circulation, the mother's immune system may recognize these cells as foreign and produce antibodies against the Rh factor. This process is known as sensitization. In subsequent pregnancies, if the mother again carries an Rh+ fetus, the pre-formed antibodies can cross the placenta and attack the fetal red blood cells. This can lead to hemolysis, or the destruction of red blood cells, resulting in anemia, jaundice, and other serious complications in the newborn.

Understanding this mechanism is essential in maternal-fetal medicine, as prophylactic treatment with Rh immunoglobulin (RhoGAM) can prevent the sensitization process, thereby protecting future pregnancies from HDN.