Red blood cell antibody screening is used to detect antibodies other than those directed against antigens A and B. This screening is particularly important in pregnant women who are Rh-negative if the father is Rh-positive. In this situation, the fetus may be Rh-negative or Rh-positive. If the fetus is Rh-negative, there is no problem of incompatibility between the antibodies in the mother’s blood and the fetus’s red blood cells. If the red blood cells of an Rh-positive fetus come into contact with the mother’s Rh-negative blood, the mother will consider these red blood cells as foreign and “record” this concept in the memory of the cells that make the antibodies. It is during a subsequent pregnancy that the mother’s antibodies could react with the red blood cells of a new Rh-positive fetus. This reaction can destroy a significant number of the fetus’s red blood cells and cause a miscarriage or severe jaundice in the newborn.
Hemolysis can also occur like this as a result of a transfusion of “foreign” blood, but special precautions taken by blood banks before any transfusion significantly limit this possibility.