Asthma at 8 years of age in children born by cesarean section

Caroline Roduit ¹, Salome Scholtens ², Johan C de Jongste ³, Alet H Wijga ¹, Jorrit Gerritsen ⁴, Dirkje S Postma ⁵, Bert Brunekreef ², Maarten O Hoekstra ⁶, Rob Aalberse ⁷ and Henriette A Smit ^1*

¹ National Institute for Public Health and the Environment, Bilthoven, Netherlands
² Institute for Risk Assessment Sciences, Utrecht University, Netherlands
³ Department of Pediatrics, Division of Respiratory Medicine, Erasmus MC – Sophia, Rotterdam, Netherlands
⁴ Beatrix Children’s Hospital, University Medical Centre Groningen, Netherlands
⁵ University Medical Centre Groningen, Netherlands
⁶ Centre for Paediatric Allergology, Wilhelmina Children's Hospital, Netherlands
⁷ Sanquin Research, Amsterdam, Netherlands

^* To whom correspondence should be addressed. E-mail: jet.smit{at}rivm.nl.

Accepted 7 September 2008

Abstract

Background: Cesarean section might be a risk factor for asthma due to a delayed microbial colonization, but the association remains controversial.

Objective: To investigate prospectively whether children born by cesarean section are more at risk of having asthma in childhood, and sensitization at the age of 8 years taking into account the parental allergic status.

Methods: We studied 2,917 children, who participated in a birth cohort study and followed for 8 years. The definition of asthma included wheeze, dyspnea and prescription of inhaled steroids. In a subgroup (n=1,454), serum IgE antibodies for inhalant and food allergens were measured at 8 years.

Results: In the total study population, 12.4% (362) of the children had asthma at the age of 8 years. Cesarean section, with a total prevalence of 8.5%, was associated with an increased risk of asthma (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.27-2.51). This association was stronger among predisposed children (with two allergic parents: OR, 2.91; 95% CI, 1.20-7.05; with only one: OR, 1.86; 95% CI, 1.12-3.09) than in children with non-allergic parents (OR, 1.36; 95% CI, 0.77-2.42). The association between cesarean section and sensitization at the age of 8 years was significant only in children of non-allergic parents (OR, 2.14; 95% CI, 1.16-3.98).

Conclusions: Children born by cesarean section have a higher risk of asthma than those born by vaginal delivery, particularly children of allergic parents. Cesarean section increases the risk for sensitization to common allergens, in children with non-allergic parents only.