If her unborn child is Rh positive the antibody may cross the placenta and bind to fetal red cells which will be destroyed by the fetal spleen. There are many factors on the surface of red blod cells which can provoke the production of antibody. If the antibody is able to cross the placenta then the fetus may be at risk for hemolytic disease. The numerous antigens on the surface of red blood cells have been placed into groups. The sensitized mother produces antibody that crosses the placenta and coats D-positive fetal red cells which are then destroyed in the fetal spleen.
Severe hemolysis causes the fetus to call upon the spleen and liver to produce more red cells.
Screening Initial blood type and screening for antibodies is part of routine prenatal care. The evaluation of a positive antibody screen should include identification of the antibody and its titer. There are several classes of antibodies. If the antibody can be identifed as an IgM then it does not cross the placenta and there is no risk of hemolysis to the fetus. The method used should be stated as the titer will vary according to the method.