title: Sex of the baby and risk of gestational diabetes mellitus in the mother: a systematic review and meta-analysis.
abstract: OBJECTIVE
  It has recently emerged that carrying a male fetus may be associated with poorer maternal beta cell function and an increased risk of gestational diabetes mellitus (GDM). Recognising that the overall impact of fetal sex on maternal glucose metabolism is likely to be subtle, we sought to perform a systematic review and meta-analysis of observational studies to obtain a robust estimate of the incremental maternal risk of GDM associated with the sex of the baby.
  
  
  METHODS
  We searched PubMed and EMBASE to identify observational studies published between 1 January 1950 and 4 April 2015 that reported data on fetal sex and the prevalence of GDM. Two independent reviewers extracted the data and pooled estimates of the RR were calculated by a random-effects model. We considered male fetus as the exposure and prevalence of GDM as the outcome of interest.
  
  
  RESULTS
  We identified 320 studies through electronic searches and nine studies through manual searches. Twenty studies met the inclusion criteria, yielding data on 2,402,643 women. Pooled analysis of these studies demonstrated an increased risk of GDM in women carrying a male fetus compared with women carrying a female fetus (RR 1.04; 95% CI 1.02, 1.06). This result was confirmed in a sensitivity analysis including only studies that applied a stringent definition of GDM (RR 1.03; 95% CI 1.01, 1.06) (I(2) = 0%, p = 0.66).
  
  
  CONCLUSIONS
  Pregnant women carrying a boy have a 4% higher relative risk of GDM than those carrying a girl. The fetus thus may have previously unsuspected effects on maternal glucose metabolism in pregnancy.
authors.affiliation: Department of Medicine, University of Toronto, Toronto, ON, Canada.
authors.forename: Diana
authors.initials: D
authors.lastname: Jaskolka
authors.affiliation: Department of Medicine, University of Toronto, Toronto, ON, Canada.|Division of Endocrinology, University of Toronto, Toronto, ON, Canada.|Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, 60 Murray Street, Suite L5-029, Mailbox-21, Toronto, ON, Canada, M5T 3L9.|Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Ravi
authors.initials: R
authors.lastname: Retnakaran
authors.affiliation: Department of Medicine, University of Toronto, Toronto, ON, Canada.|Division of Endocrinology, University of Toronto, Toronto, ON, Canada.|Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, 60 Murray Street, Suite L5-029, Mailbox-21, Toronto, ON, Canada, M5T 3L9.|Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Bernard
authors.initials: B
authors.lastname: Zinman
authors.affiliation: Department of Medicine, University of Toronto, Toronto, ON, Canada. ckramer@mtsinai.on.ca.|Division of Endocrinology, University of Toronto, Toronto, ON, Canada. ckramer@mtsinai.on.ca.|Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, 60 Murray Street, Suite L5-029, Mailbox-21, Toronto, ON, Canada, M5T 3L9. ckramer@mtsinai.on.ca.
authors.forename: Caroline K
authors.initials: CK
authors.lastname: Kramer
mesh_terms: D016640:Diabetes, Gestational / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008431:Maternal-Fetal Exchange / Q000502:physiology*; D011247:Pregnancy; D012307:Risk Factors; D012737:Sex Factors
keywords: Beta cell function; Fetal sex; Gestational diabetes; Male fetus; Meta-analysis; Systematic review