The author presents observations on the occurrence of severe fetal-maternal transfusion in two cases, in one of which both the child and the mother were of the same blood group. In the second case, conventional investigating procedures based upon differential agglutination failed to demonstrate fetal erythrocytes in the maternal circulation. In this case, the elution of adult red cell hemoglobin on fixed smears prepared from the mother’s peripheral blood, confirmed the presence of her infant’s intact red cell in her circulation.

In an additional study, labor-induced transplacental passage of fetal red cells was investigated and a brief discussion of the diagnostic procedure is offered.