Erythroblastosis Fetalis due to maternal–fetal Rh incompatibility. (Pathogenesis)
Immunization of an Rh-negative mother with Rh-positive erythrocytes in the first pregnancy leads to formation of anti-Rh antibodies of the immunoglobulin (Ig) G type. These antibodies cross the placenta and damage the Rh-positive fetus in subsequent pregnancies.