title: Cesarean section and the risk of pediatric Crohn's disease.
abstract: BACKGROUND
  Crohn's disease (CD) could involve an inappropriate immune response against normal bowel flora. Disrupted or atypical patterns of microbial bowel colonization may impair development of homeostasis between gut flora and the immune system. Perinatal microbial exposures may be particularly important in stimulating intestinal immune recognition. As birth by cesarean section is thought to represent an atypical pattern of early bowel colonization, we examined its association with pediatric CD.
  
  
  METHODS
  Some 1536 patients diagnosed with pediatric CD and 15,439 controls matched by delivery unit, week of birth, sex, and born between 1973 and 2006 were identified through Swedish registers. The association of birth by cesarean section with pediatric CD was examined using conditional logistic regression, with stratification by sex and adjustment for parental socioeconomic index and maternal infections during pregnancy.
  
  
  RESULTS
  Birth by cesarean section is associated with a modestly increased risk for pediatric CD among boys (odds ratio [OR] = 1.25, 95% confidence interval [CI] 1.01-1.54) but not girls, (OR = 0.99, 95% CI 0.76-1.29) and elective cesarean section is associated with a modest increased risk for the entire population (OR = 1.36, 95% CI 1.02-1.80).
  
  
  CONCLUSIONS
  This study does not suggest that the delivery procedure should be altered, but the findings may be of etiological significance in CD, indicating a potential role for perinatal exposures associated with delivery mode. Although the sex difference may have arisen by chance, the modestly increased CD risk for boys delivered by cesarean section is consistent with sex-specific differences in susceptibility to some exposures.
authors.affiliation: Department of Women and Child Health, Karolinska Institutet, Stockholm, Sweden. petter.malmborg@karolinska.se
authors.forename: Petter
authors.initials: P
authors.lastname: Malmborg
authors.forename: Shahram
authors.initials: S
authors.lastname: Bahmanyar
authors.forename: Lena
authors.initials: L
authors.lastname: Grahnquist
authors.forename: Hans
authors.initials: H
authors.lastname: Hildebrand
authors.forename: Scott
authors.initials: S
authors.lastname: Montgomery
mesh_terms: D000293:Adolescent; D000328:Adult; D002585:Cesarean Section / Q000009:adverse effects* / Q000706:statistics & numerical data; D002648:Child; D002675:Child, Preschool; D003424:Crohn Disease / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D012306:Risk; D012737:Sex Factors; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult