A number of transfusion accidents in pregnancy have been reported in the literature, even though the donor, frequently the husband, was in the same blood group as the patient.1In one instance analyzed by Levine and Stetson2it was assumed that the accident could be attributed to an agglutinin resulting from immunization of the mother by factors in the fetus inherited from the father. Analysis of a series of 12 cases in which atypical agglutinins could be demonstrated revealed the significant fact that these patients presented obstetric histories characterized by a number of complications such as toxemia, macerated fetus, repeated abortions, miscarriages or stillbirths.3 Recently 5 additional patients with atypical agglutinins were observed, 3 of whom gave birth to infants suffering from erythroblastosis foetalis. The obstetric histories of these cases are so striking as to merit brief mention. One patient, J. L. (decigravida, sextipara), now pregnant and