Asthma and atopy in children born by caesarean section: effect modification by family history of allergies – a population based cross-sectional study

Asthma outcomes were assessed cross-sectionally in 2216 children at age 8 on the basis of parents’ responses to the ISAAC questionnaire whilst skin prick tests to eleven aeroallergens were also performed in a subgroup of 746 children. Adjusted odds ratios of asthma and atopy by mode of delivery were estimated in multivariable logistic models while evidence of effect modification was examined by introducing interaction terms in the models.After adjusting for potential confounders, children born by C/S appeared significantly more likely than those born vaginally to report ever wheezing (OR 1.36, 95% CI 1.07-1.71), asthma diagnosis (OR 1.41, 95% CI 1.09-1.83) and be atopic (OR 1.67, 95% CI 1.08-2.60). There was modest evidence that family history of allergies may modify the effect of C/S delivery on atopy (p for effect modification=0.06) but this was not the case for the asthma outcomes. Specifically, while more than a two-fold increase in the odds of being a topic was observed in children with a family history of allergies if born by C/S (OR 2.62, 95% CI 1.38-5.00), no association was observed in children without a family history of allergies (OR 1.16, 95% CI 0.64-2.11).Birth by C/S is associated with asthma and atopic sensitization in childhood. The association of C/S and atopy appears more pronounced in children with family history of allergies.In recent decades, there has been an increase in the proportion of children born by caesarean section (C/S) beyond the recommended by WHO level of 15%. Rises were mostly observed in developed nations such as the United States of America [1], United Kingdom [2] and other European countries [3]. In England, for example, in year 2010, 23.4% of singletons were delivered by C/S [4]. In Cyprus, the Perinatal Health Survey performed in year 2007 by the Statistical Services of the country estimated the C/S rate to be as high as 50.9% [5]. During this period, a rise in the prevalence of asthma and allergies was also observed and, to d