['The birth of a boy is significantly more common than a girl prior to secondary recurrent miscarriage (SRM) and is associated with a poorer chance of a subsequent live birth. Children born after SRM are more likely to be girls. High-titer antisera specific for male antigens (H-Y) have been shown to arrest development of male bovine embryos efficiently. We consequently questioned the role of H-Y antibodies in women with SRM.', 'Serum samples from patients with unexplained SRM (n = 84), unexplained primary recurrent miscarriage (PRM) (n = 12) and healthy women (n = 37) were obtained. The samples were taken during pregnancy (gestational weeks 4-5) for 77 (80%) of the patients. Enzyme-linked immunosorbent assay was used to detect immunoglobulin G antibodies that specifically recognized any of the five recombinant H-Y proteins (EIF1AY, RPS4Y1, ZFY, DDX3Y and UTY) and their H-X homologs.', 'H-Y-specific antibodies were more frequent in SRM patients (46%) compared with female controls (19%, P = 0.004) and PRM patients (8%, P = 0.01). The presence of H-Y antibodies in early pregnancy was associated with a low male: female birth ratio among the subsequent live births, as only 12% of children born to H-Y antibody-positive patients were boys compared with 44% boys born to H-Y antibody negative patients (P = 0.03).'] Are h-Y antibody titers increased in unexplained secondary recurrent miscarriage patients and associated with low male : female ratio in subsequent live births?