Cesarean section and the risk of pediatric Crohn's disease

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.