What causes hemolytic disease of the newborn (HDN)?

Hemolytic disease of the newborn (HDN) primarily occurs due to blood type incompatibility between the mother and her fetus. In the context of this condition, the situation that is most common and particularly problematic is when the mother is Rh-negative and the fetus is Rh-positive.

In this scenario, during pregnancy or delivery, fetal red blood cells can enter the maternal circulation, leading the mother’s immune system to recognize these cells as foreign due to the Rh factor. The mother's immune system then produces antibodies against the Rh-positive blood cells. If these antibodies cross the placenta, they can attack the fetal red blood cells, resulting in hemolysis (destruction of red blood cells) and subsequent anemia in the newborn.

This specific incompatibility highlights the importance of maternal blood typing and monitoring during pregnancy to prevent serious complications associated with HDN. It can lead to conditions such as jaundice, severe anemia, or even intrauterine fetal demise if not managed properly.

While maternal blood type incompatibility is a broader phenomenon, the scenario where the mother is Rh-negative and the fetus is Rh-positive directly illustrates the mechanism most commonly responsible for HDN. This recognition allows healthcare providers to take preventative measures, such as administering Rh immunoglobulin to the mother