title: Asthma at 8 years of age in children born by caesarean section.
abstract: BACKGROUND
  Caesarean section might be a risk factor for asthma because of delayed microbial colonisation, but the association remains controversial. A study was undertaken to investigate prospectively whether children born by caesarean section are more at risk of having asthma in childhood and sensitisation at the age of 8 years, taking into account the allergic status of the parents.
  
  
  METHODS
  2917 children who participated in a birth cohort study were followed for 8 years. The definition of asthma included wheeze, dyspnoea and prescription of inhaled steroids. In a subgroup (n = 1454), serum IgE antibodies for inhalant and food allergens were measured at 8 years.
  
  
  RESULTS
  In the total study population, 12.4% (n = 362) of the children had asthma at the age of 8 years. Caesarean section, with a total prevalence of 8.5%, was associated with an increased risk of asthma (OR 1.79; 95% CI 1.27 to 2.51). This association was stronger among predisposed children (with two allergic parents: OR 2.91; 95% CI 1.20 to 7.05; with only one: OR 1.86; 95% CI 1.12 to 3.09) than in children with non-allergic parents (OR 1.36; 95% CI 0.77 to 2.42). The association between caesarean section and sensitisation at the age of 8 years was significant only in children of non-allergic parents (OR 2.14; 95% CI 1.16 to 3.98).
  
  
  CONCLUSIONS
  Children born by caesarean section have a higher risk of asthma than those born by vaginal delivery, particularly children of allergic parents. Caesarean section increases the risk for sensitisation to common allergens in children with non-allergic parents only.
authors.affiliation: Centre for Prevention and Health Services Research, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: C
authors.initials: C
authors.lastname: Roduit
authors.forename: S
authors.initials: S
authors.lastname: Scholtens
authors.forename: J C
authors.initials: JC
authors.lastname: de Jongste
authors.forename: A H
authors.initials: AH
authors.lastname: Wijga
authors.forename: J
authors.initials: J
authors.lastname: Gerritsen
authors.forename: D S
authors.initials: DS
authors.lastname: Postma
authors.forename: B
authors.initials: B
authors.lastname: Brunekreef
authors.forename: M O
authors.initials: MO
authors.lastname: Hoekstra
authors.forename: R
authors.initials: R
authors.lastname: Aalberse
authors.forename: H A
authors.initials: HA
authors.lastname: Smit
mesh_terms: D001249:Asthma / Q000209:etiology*; D002585:Cesarean Section; D002648:Child; D002675:Child, Preschool; D002908:Chronic Disease; D015331:Cohort Studies; D004417:Dyspnea / Q000209:etiology; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000209:etiology; D007073:Immunoglobulin E / Q000378:metabolism; D008297:Male; D011379:Prognosis; D011446:Prospective Studies; D012135:Respiratory Sounds / Q000209:etiology; D012307:Risk Factors
chemical_list: D007073:Immunoglobulin E