11/08/2024
Hemolytic disease of the newborn (HDN) is a blood disorder in a fetus or newborn infant. In some infants, it can be fatal.
Normally, red blood cells (RBCs) last for about 120 days in the body. In this disorder, RBCs in the blood are destroyed quickly and thus do not last as long.
Causes
During pregnancy, RBCs from the unborn baby can cross into the mother's blood through the placenta. HDN occurs when the immune system of the mother sees a baby's RBCs as foreign. Antibodies then develop against the baby's RBCs. These antibodies attack the RBCs in the baby's blood and cause them to break down too early.
HDN may develop when a mother and her unborn baby have different blood types. The types are based on small substances (antigens) on the surface of the blood cells.
There is more than one way in which the unborn baby's blood type may not match the mother's.
A, B, AB, and O are the 4 major blood group antigens or types. This is the most common form of a mismatch. In most cases, this is not very severe.
Rh is short for the "rhesus" antigen or blood type. People are either positive or negative for this antigen. If the mother is Rh-negative and the baby in the womb has Rh-positive cells, her antibodies to the Rh antigen can cross the placenta and cause very severe anemia in the baby. It can be prevented in most cases.
There are other, much less common, types of mismatch between minor blood group antigens. Some of these can also cause severe problems.
