title: Caesarean section is associated with an increased risk of childhood-onset type 1 diabetes mellitus: a meta-analysis of observational studies.
abstract: OBJECTIVE
  The aim of this study was to investigate the evidence of an increased risk of childhood-onset type 1 diabetes in children born by Caesarean section by systematically reviewing the published literature and performing a meta-analysis with adjustment for recognised confounders.
  
  
  METHODS
  After MEDLINE, Web of Science and EMBASE searches, crude ORs and 95% CIs for type 1 diabetes in children born by Caesarean section were calculated from the data reported in each study. Authors were contacted to facilitate adjustments for potential confounders, either by supplying raw data or calculating adjusted estimates. Meta-analysis techniques were then used to derive combined ORs and to investigate heterogeneity between studies.
  
  
  RESULTS
  Twenty studies were identified. Overall, there was a significant increase in the risk of type 1 diabetes in children born by Caesarean section (OR 1.23, 95% CI 1.15-1.32, p < 0.001). There was little evidence of heterogeneity between studies (p = 0.54). Seventeen authors provided raw data or adjusted estimates to facilitate adjustments for potential confounders. In these studies, there was evidence of an increase in diabetes risk with greater birthweight, shorter gestation and greater maternal age. The increased risk of type 1 diabetes after Caesarean section was little altered after adjustment for gestational age, birth weight, maternal age, birth order, breast-feeding and maternal diabetes (adjusted OR 1.19, 95% CI 1.04-1.36, p = 0.01).
  
  
  CONCLUSIONS
  This analysis demonstrates a 20% increase in the risk of childhood-onset type 1 diabetes after Caesarean section delivery that cannot be explained by known confounders.
authors.affiliation: Department of Epidemiology and Public Health, School of Medicine and Dentistry, Queen's University Belfast, Grosvenor Road, Belfast, BT12 6BJ, UK. c.cardwell@qub.ac.uk
authors.forename: C R
authors.initials: CR
authors.lastname: Cardwell
authors.forename: L C
authors.initials: LC
authors.lastname: Stene
authors.forename: G
authors.initials: G
authors.lastname: Joner
authors.forename: O
authors.initials: O
authors.lastname: Cinek
authors.forename: J
authors.initials: J
authors.lastname: Svensson
authors.forename: M J
authors.initials: MJ
authors.lastname: Goldacre
authors.forename: R C
authors.initials: RC
authors.lastname: Parslow
authors.forename: P
authors.initials: P
authors.lastname: Pozzilli
authors.forename: G
authors.initials: G
authors.lastname: Brigis
authors.forename: D
authors.initials: D
authors.lastname: Stoyanov
authors.forename: B
authors.initials: B
authors.lastname: Urbonaite
authors.forename: S
authors.initials: S
authors.lastname: Sipetić
authors.forename: E
authors.initials: E
authors.lastname: Schober
authors.forename: C
authors.initials: C
authors.lastname: Ionescu-Tirgoviste
authors.forename: G
authors.initials: G
authors.lastname: Devoti
authors.forename: C E
authors.initials: CE
authors.lastname: de Beaufort
authors.forename: K
authors.initials: K
authors.lastname: Buschard
authors.forename: C C
authors.initials: CC
authors.lastname: Patterson
mesh_terms: D000328:Adult; D017668:Age of Onset; D001722:Birth Order; D001724:Birth Weight; D002585:Cesarean Section / Q000009:adverse effects*; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology* / Q000235:genetics; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D011247:Pregnancy; D012307:Risk Factors