Mode of delivery and childhood hospitalizations for asthma and other wheezing disorders

BackgroundObservationally, delivery by Caesarean section is associated with higher risk of childhood asthma and wheeze in developed Western settings, but associations are less consistent in other settings. ObjectiveTo examine the association of mode of delivery with hospitalizations for asthma and other wheezing disorders in a developed non-Western setting with high rates of Caesarean section. MethodsUsing Cox regression, we examined the adjusted association of mode of delivery with public hospital admissions for asthma, bronchitis, and bronchiolitis (International Classification of Diseases, Ninth Version Clinical Modification 466, 490 and 493) from 9days to 12years of age in a population-representative prospective birth cohort of 8327 Chinese children in Hong Kong. Confounders included sex, birth and parental characteristics, and socio-economic position (SEP). ResultsDelivery by Caesarean section accounted for 27% of all births and was not clearly associated with hospitalizations for asthma and other wheezing disorders to 12years [hazard ratio (HR) 1.11, 95% confidence interval (CI) 0.91 to 1.36] compared to vaginal delivery. Similarly, there were no clear associations to 2years (HR 1.07, 95% CI 0.83 to 1.38) or 6years (HR 1.12, 95% CI 0.91 to 1.37), although we cannot rule out residual confounding by SEP. Conclusions and Clinical RelevanceWe cannot rule out an association, but our findings suggest that the observed associations of delivery by Caesarean section with childhood wheezing disorders may vary with setting and may not be biologically mediated. Further studies with different designs are needed to clarify the role of the microbiome and mode of delivery in the aetiology of asthma and other childhood wheezing disorders.