title: Caesarean section and allergic manifestations: insufficient evidence of association found in population-based study of children aged 1 to 4 years.
abstract: OBJECTIVE
  To provide evidence on the association between caesarean section and allergic manifestations in an unselected child population.
  
  
  METHODS
  Research focused on all children aged from one to 4 years (N = 4779), born between April 2001 and March 2005 and living in the province of South Karelia, Finland. They were identified from the nationwide population register. Questionnaire data on 3181 participants were individually merged with allergy test results (skin prick tests, IgE antibodies and open food challenges) from all patient records.
  
  
  RESULTS
  Compared with vaginal delivery, the adjusted relative incidence of positive allergy tests (with 95% confidence intervals, CI) in children born by caesarean section was 1.14 (0.79, 1.65) for food, 1.16 (0.66, 2.05) for animals, 0.94 (0.46, 1.92) for pollen and 1.19 (0.87, 1.63) for any allergens. The corresponding adjusted prevalence odds ratios (with 95% CI) of physician-diagnosed allergic manifestations were 1.15 (0.80, 1.63) for food allergy, 0.90 (0.47, 1.59) for pollen allergy or hay fever, 1.00 (0.75, 1.31) for atopic eczema, 0.96 (0.53, 1.65) for asthma and 1.08 (0.85, 1.38) for any allergic manifestation.
  
  
  CONCLUSIONS
  Insufficient evidence was found in our population for any association between birth by caesarean section and allergic manifestations. Further evidence from unselected populations, with longer follow-up periods, is needed.
authors.affiliation: South Karelia District of Social and Health Services, Lappeenranta, Finland. kaisa.pyrhonen@oulu.fi
authors.forename: K
authors.initials: K
authors.lastname: Pyrhönen
authors.forename: S
authors.initials: S
authors.lastname: Näyhä
authors.forename: L
authors.initials: L
authors.lastname: Hiltunen
authors.forename: E
authors.initials: E
authors.lastname: Läärä
mesh_terms: D002585:Cesarean Section / Q000009:adverse effects*; D002675:Child, Preschool; D005260:Female; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D015994:Incidence; D007223:Infant; D053208:Kaplan-Meier Estimate; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D015995:Prevalence; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors; D011795:Surveys and Questionnaires
keywords: Allergy; Asthma; Atopy; Caesarean section; Epidemiology