title: Recurrent miscarriage and birth sex ratio.
abstract: OBJECTIVE
  To examine the relationship between birth sex ratio and unexplained recurrent miscarriage (RM).
  
  
  METHODS
  Retrospective, 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.
  
  
  RESULTS
  In 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.
  
  
  CONCLUSIONS
  There was a subtle relationship between the sex of the first and subsequent births and secondary recurrent miscarriage, but not primary recurrent miscarriage.
authors.affiliation: The Jessop Wing, Sheffield Teaching Hospitals NHS Trust, Sheffield, United Kingdom; Center for Reproductive Medicine, Dalian Obstetrics & Gynecology Hospital, Dalian, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Li
authors.affiliation: The Jessop Wing, Sheffield Teaching Hospitals NHS Trust, Sheffield, United Kingdom; Center for Reproductive Medicine, Sir Run Run Shaw Hospital, Zhejiang University, China.
authors.forename: Liu
authors.initials: L
authors.lastname: Liu
authors.affiliation: The Jessop Wing, Sheffield Teaching Hospitals NHS Trust, Sheffield, United Kingdom.
authors.forename: Beiyu
authors.initials: B
authors.lastname: Liu
authors.affiliation: St Mary's Hospital, London, United Kingdom.
authors.forename: Sotiris
authors.initials: S
authors.lastname: Saravelos
authors.affiliation: The Jessop Wing, Sheffield Teaching Hospitals NHS Trust, Sheffield, United Kingdom. Electronic address: tinchiu.li@gmail.com.
authors.forename: Tinchiu
authors.initials: T
authors.lastname: Li
mesh_terms: D000026:Abortion, Habitual / Q000453:epidemiology* / Q000235:genetics; D005260:Female; D006801:Humans; D050498:Live Birth / Q000453:epidemiology; D008297:Male; D011247:Pregnancy; D011379:Prognosis; D012744:Sex Ratio; D050497:Stillbirth / Q000453:epidemiology*; D006113:United Kingdom / Q000453:epidemiology
keywords: First birth; Recurrent miscarriage; Sex ratio; Stillbirth; Subsequent birth