A case of unexplained mild Rh (D) haemolytic disease in utero

This report describes the case of a patient with a history of HDN complicated by fetal losses, in which the alloantibody in this particular pregnancy did not appear to cause HDN in utero. No protective HLA-DR antibodies could be demonstrated, and transport of IgG across the placenta appeared to be normal. The infant's red cells possessed a normal D antigen and his mononuclear phagocyte system appeared unimpaired. However, the number of molecules of IgG bound in vivo per fetal red cell was below the level usually associated with significant haemolysis and HDN.