Recurrent miscarriage and birth sex ratio

ObjectiveTo examine the relationship between birth sex ratio and unexplained recurrent miscarriage (RM).Study designRetrospective, observational study including a total of 138 women with primary recurrent miscarriage (PRM) and 170 women with secondary recurrent miscarriage (SRM) in a tertiary referral recurrent miscarriage clinic between 1992 and 2010. The sex ratio of the first birth and subsequent birth were the main outcome measures.ResultsIn women with SRM: (i) The male:female sex ratio of the first stillbirth was 10:2, significantly (OR = 4.76) higher than the male:female sex ratio of 1.05 among all births in UK. (ii) When the first born was a male, the male:female sex ratio of the subsequent birth was 21:35, significantly (OR = 0.57) lower than the sex ratio among the general population. (iii) A male firstborn did not affect the chance of a subsequent live-birth. The findings did not apply to sex ratio in primary RM.ConclusionThere was a subtle relationship between the sex of the first and subsequent births and secondary recurrent miscarriage, but not primary recurrent miscarriage.