Maternal-fetal interaction in the ABO system: A comparative analysis of healthy mothers and couples with recurrent spontaneous abortion suggests a protective effect of B incompatibility

We investigated the possible differential effects of A and B blood group ma terno-fetal incompatibility on human fertility through a comparative analys is of couples with recurrent spontaneous abortion (RSA) and healthy mothers . ABO phenotype was determined in 5180 healthy mothers and their newborn ba bies from the population of Sassari (Sardinia) and in 1359 healthy puerpera e (women who have just given birth) from the population of Rome. Mother-new born joint ABO distribution in healthy mothers was compared with wife-husba nd joint ABO distribution in RSA couples. Distortions from expected distrib ution were evaluated by symmetry analysis. In both RSA couples and healthy mothers significant deviation from expected symmetry patterns were observed . Deviations in RSA are in the opposite direction to those observed in heal thy puerperae. The most important difference observed concerned the symmetr ic joint phenotypes mother (women) A / infant (husband) B (B incompatible) and mother (women) B / infant (husband) A (A incompatible). A low number of B incompatible in RSA couples and a high number of B incompatible in healt hy mothers was observed. The phenomenon is much more evident in women aged 24-28 years, a period of maximum fecundity. It is possible that the presenc e of anti-B immunoglobulin in the mother might have a protective effect aga inst fetal loss in some cases of mother-infant ABO incompatibility.