Sex differences of abortuses and neonates in women with allo-immune recurrent abortions

To investigate the possible association of recurrent spontaneous abortions (RSA) of immune aetiologies with neonatal sex differences, karyotyping of abortuses from allo-immune RSA and epidemiological studies on the sex differences of neonates from sporadic aborters was carried out. Allo-immune disorders, as diagnosed by an increased number of shared HLA class II loci and reduced blocking activity of the woman's serum in mixed lymphocyte reaction, were found almost twice (54.9%) as often as auto-immune disorders (29.9%) among a total of 244 women with RSA. Of 33 abortuses karyotyped from women with RSA, 69.7% showed normal female karyotypes, while only 6.1% had normal male karyotypes, indicating that female fetuses are more prone to abort than males. Epidemiological studies revealed that boys were born at a significantly greater incidence of 58.1% in 221 women with a history of sporadic abortion than 47.6% in 893 women with no history of abortion. Moreover, the proportion of women giving birth to boys only was consistently and significantly higher, regardless of repeated deliveries, in sporadic aborters (36.7%) than in women with no history of abortion (19.6%), showing that more boys were born than girls to women with sporadic abortion. It is concluded that male fetuses are more likely to survive than females in allo-immune RSA due to allo-immune reproductive wastage of chromosomally normal female concept in early human pregnancy, and that allo-immune RSA makes up the highest proportion of unexplained RSA.