title: Mode of delivery and childhood hospitalizations for asthma and other wheezing disorders.
abstract: BACKGROUND
  Observationally, 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.
  
  
  OBJECTIVE
  To 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.
  
  
  METHODS
  Using 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 9 days to 12 years 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).
  
  
  RESULTS
  Delivery by Caesarean section accounted for 27% of all births and was not clearly associated with hospitalizations for asthma and other wheezing disorders to 12 years [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 2 years (HR 1.07, 95% CI 0.83 to 1.38) or 6 years (HR 1.12, 95% CI 0.91 to 1.37), although we cannot rule out residual confounding by SEP.
  
  
  CONCLUSIONS
  We 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.
authors.affiliation: School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: J Y Y
authors.initials: JY
authors.lastname: Leung
authors.affiliation: Department of Paediatrics, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, China.
authors.forename: A M
authors.initials: AM
authors.lastname: Li
authors.affiliation: School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: G M
authors.initials: GM
authors.lastname: Leung
authors.affiliation: School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.|CUNY School of Public Health, Hunter College, New York, NY, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Schooling
mesh_terms: D001249:Asthma / Q000453:epidemiology* / Q000209:etiology*; D002585:Cesarean Section / Q000009:adverse effects; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D036861:Delivery, Obstetric / Q000379:methods; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006760:Hospitalization; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D062486:Public Health Surveillance; D012135:Respiratory Sounds / Q000209:etiology*; D012307:Risk Factors
keywords: asthma; caesarean section; children; cohort study; delivery; wheeze