Delivery mode and the incidence of atopic sensitization and food allergy in a Finnish child population

Abstract Background: Caesarean section (CS) has been associated with an increased risk of subsequent atopic diseases, particularly asthma and respiratory allergies, but controversial findings have also been reported. Our aim was to clarify the association between the delivery mode and longitudinal (atopic) outcomes. Methods: The target population was identified from the population register and comprised all children born between 2001 and 2006 and living in the province of South Karelia, Finland (N = 5564). The information on the delivery mode was available for 5552 children from the Finnish Medical Birth Register. Results of allergy tests (skin prick tests, specific IgE and open food challenges, OFCs) were collected from patient records of all healthcare units in the area. Results: By 12 years of age, the cumulative incidence of atopic sensitization was 15% for those born by normal vaginal delivery (VD), 20% (adjusted RR 1.28; 95% CI 0.99–1.65) by assisted VD, 20% (adjusted RR 1.28; 95% CI 1.02–1.61) by elective CS and 20% (adjusted RR 1.24; 95% CI 0.99–1.56) by others, for example emergency CS. Among the offspring of mothers without atopic diseases, the incidence of food allergy (positive OFC) was 6% for those born by elective CS and 2% for those born by normal VD (adjusted RR 2.41; 95% CI 1.19–4.88), while the respective incidences were 5% and 6% (adjusted RR 0.82; 95% CI 0.33–2.06) among the offspring of mothers with atopic diseases. Conclusion: By adolescence, the cumulative incidences of atopic sensitization was highest among those born by assisted VD or CS. The incidence of food allergy was highest among those born by elective CS among the offspring of mothers without atopic diseases