(746) Obstetrical mode of delivery and asthma in childhood and adolescence: findings from Millennium Cohort Study

To examine the association between mode of delivery (in particular caesarean section) and childhood asthma, persistent asthma and adolescent onset asthma.

Study Design: We used maternal-reported data from The Millennium Cohort Study, a nationally representative longitudinal study of children born in the United Kingdom. Data on mode of delivery and potential confounders were collected at age 9 months. Mode of delivery was categorised as spontaneous vaginal delivery, assisted vaginal delivery, induced vaginal delivery, emergency caesarean section, planned caesarean section and induced caesarean section. Outcomes of interest included asthma at age 7, 11 or 14 years, persistent asthma (asthma at ages 7, 11 and 14 years) and adolescent onset asthma (asthma at age 14 years, but not prior) using the International Study of Asthma and Allergies in Childhood questionnaire. Crude and adjusted logistic regression were used to examine the association between mode of delivery and asthma, adjusting for several maternal and socio-economic factors, and complications of pregnancy.

Results:

There were 18213 singleton mother-child pairs included at baseline, 12687 at age 7; 11055 at age 11 and 10745 at age 14. Adjusted logistic regression suggested an association between emergency caesarean section and asthma at ages 7 years (OR: 1.27, 95% CI: 1.06-1.51), 11 years (OR: 1.39, 95% CI: 1.15-1.67)  and 14 years (OR: 1.27, 95% CI: 1.01-1.59). Induced vaginal delivery was associated with asthma at age 11 years only (OR: 1.17, 95% CI: 1.03-1.33), while induced caesarean section was associated with persistent asthma (OR: 1.42, 95% CI: 1.06-1.90). No significant associations were observed between elective section and asthma in the offspring.

Conclusion:

Children born by an emergency caesarean section, but not elective had an increased likelihood of asthma diagnosis. These results suggest the association is due to confounding by indication and unlikely to be causal.