“…This finding would appear to confer some advantage upon the secretor fetuses in heterospecific pregnancies. McNeil et al [1957] found that among couples in which the wife had suffered two or more spontaneous abortions: (a) immune antibodies in the ABO system were usually present in the wife; (b) mother, father, or both were generally aber rant secretors (defined as persons of group A or B who secrete only one blood group factor rather than the expected two) ; (c) the matings were generally incompatible in the ABO system ; (d) mothers in the aborter group tended to be, if not aberrant secretors, then weak secretors or nonsecretors. F reda [1958] pointed out th at the in compatible nonsecretor fetus of a m other with immune ABO anti bodies would have less protection against these m aternal antibodies.…”