children s health issues
Hemolytic Disease of the Newborn
Rh incompatibility
The Rh factor is a molecule on the surface of red blood cells in some people. Blood is Rh-positive if a person's red blood cells have the Rh factor. Blood is Rh-negative if a person's red blood cells do not have the Rh factor. Most people are Rh-positive. When a baby has Rh-positive red blood cells and the mother has Rh-negative red blood cells, the two have Hemolytic Disease of the Fetus and Newborn . As a result, the immune system of an Rh-negative mother may recognize the Rh-positive fetus’s red blood cells as "foreign" and produce antibodies against the Rh factor on the fetus's red blood cells. This process is called Rh sensitization. When a mother has Rh antibodies, they can pass from her blood through the placenta into the fetus's blood before delivery. If the fetus is Rh-positive, the mother’s Rh antibodies can attach to and destroy (hemolyze) the fetus's red blood cells. The rapid breakdown of red blood cells begins while the fetus is still in the womb and continues after delivery. This breakdown can cause anemia. A mother who is Rh-negative can produce the Rh antibodies if she is exposed to Rh-positive red blood cells. The most common way women are exposed to Rh-positive blood is when they have a fetus who is Rh-positive. Mothers are exposed to the most blood from the fetus during delivery, so that is when most Rh sensitization occurs. Thus, most hemolytic disease happens to a fetus whose mother was sensitized during an earlier pregnancy. Mothers also can be exposed to Rh-positive blood earlier in pregnancy, for example, during a Miscarriage or Exposure may also occur outside of pregnancy, for example if the mother was transfused with Rh-positive blood at any time earlier in her life. Once the mother has been exposed and developed antibodies, problems are more likely with each subsequent pregnancy in which the fetus is Rh-positive. 