Four cohort studies were included in the review (n=15,121): three prospective birth cohort studies (n=6,168) and one retrospective cohort (n=8,953). Study size ranged from 865 to 8,953 participants. Follow-up ranged from 77 to 97%.
Two prospective studies assessed levels of food allergen-specific IgE. Both found that babies born by caesarean section were more likely to be sensitised to food allergens (using IgE measurement; different cutoff for each study). Adjustment for possible confounding factors did not affect this association.
Two studies assessed the relationship between delivery by caesarean section and symptomatic food allergy; one (retrospective) study reported no difference in food allergy diagnoses between those born by caesarean compared with vaginal birth (but did not adjust for confounders); the other (prospective) study found parent-reported food allergy was greater in those born by caesarean section.