Histocompatibility in couples with recurrent spontaneous abortion and normal fertility.

Histocompatibility between husband and wife at the HLA locus has been suggested as a determinant of recurrent spontaneous abortion. We measured the incidence of HLA antigen sharing within 12 couples with histories of unexplained recurrent abortion and in a fertile control population of 77 couples. In the recurrent abortion group, 6 of 12 (50%) of the couples shared no HLA antigens, whereas only 3 of 12 (25%) shared one antigen, 1 of 12 (8.3%) shared two antigens, and 2 of 12 (17%) shared three antigens. In the fertile group, 27 of 77 (35.1%) shared no antigens, 33 of 77 (42.8%) shared one antigen, 14 of 77 (18.2%) shared two antigens, 2 of 77 (2.6%) shared three antigens, and 1 of 77 (1.3%) shared four antigens. In 50 of these control couples who were available for complete reproductive histories, there were no significant correlations between the incidence of antigen sharing and the numbers of offspring, the incidence of spontaneous abortion, or infertility problems. Six of the women in the recurrent abortion group became pregnant during the study. Three of these (50%) delivered live infants independent of the degree of antigen sharing and without the benefit of immunologic treatment. Therefore, the degree of HLA antigen sharing did not define a population with increased pregnancy wastage or predict subsequent pregnancy outcome.