Birth by cesarean section, allergic rhinitis, and allergic sensitization among children with a parental history of atopy.

This study examined the relation between birth by caesarean delivery and atopy and allergic diseases in children at risk for atopy. After adjustment for other covariates, children born by caesarean section had 2-fold higher odds of atopy than those born by vaginal delivery (odds ratio, 2.1; 95% CI, 1.1-3.9). In multivariate analyses birth by caesarean section was significantly associated with increased odds of allergic rhinitis (odds ratio, 1.8; 95% CI, 1.0-3.1) but not with asthma. The findings suggest that caesarean delivery is associated with allergic rhinitis and atopy among children with a parental history of asthma or allergies. This could be explained by lack of contact with the maternal vaginal/faecal flora or reduced/absent labour during caesarean delivery. J Allergy Clin Immunol. 2008;122(2):274-9.