Effects of delivery mode and labor duration on the development of food sensitization in infancy.

Background: The effects of delivery mode and labor duration on the development of food sensitization (FS) in infancy remain unclear.

Objective: To elucidate the potential effects of delivery mode and labor duration on FS development by 6 months of age.

Methods: Using data from a randomized controlled trial of a birth cohort from 4 Japanese hospitals that assessed cow's milk allergy development by 6 months of age, we performed a nested case-control trial of 462 participants who had undergone the final assessment at 6 months of age. FS was defined as positive skin prick test reactions to hen's egg, cow's milk, wheat, or soy. For the primary outcome, we calculated the adjusted odds ratio of vaginal delivery (VD) relative to cesarean delivery for FS development by 6 months of age using a multivariable logistic regression analysis. For the secondary outcome, we compared labor durations between participants with and without FS using the Mann-Whitney U test.

Results: The adjusted odds ratio of VD for FS development was 2.54 (95% confidence interval, 1.32-4.87; P = .005). The median labor duration was significantly longer in participants with FS (5.7 hours, interquartile range, 2.7-10.1) than in participants without FS (4.5 hours, 1.1-8.2) (P = .01).

Conclusion: VD was considerably associated with an increased risk of FS in infancy, and longer labor durations may promote FS development.