NEW YORK (Reuters Health) – Children born by cesarean delivery are at increased risk for developing asthma, particularly if their parents have allergies, according to a report in the February issue of Thorax.

Through delayed microbial colonization, C-section has been thought to be a risk factor for asthma, although the relationship is controversial, note Dr. H. A. Smit, from the National Institute for Public Health and the Environment in Bilthoven, the Netherlands, and colleagues.

In the present study, Dr. Smit’s team analyzed data from 2917 children to assess the association between cesarean delivery and asthma or allergen sensitization at 8 years of age. In about half of the patients, serum IgE levels for inhalant and food allergens were also measured at 8 years.

Overall, 12.4% of subjects had asthma at 8 years, the researchers report, and the prevalence of c-section was 8.5%.

The odd ratio for asthma associated with cesarean delivery versus vaginal delivery was 1.79, overall. The odds ratios for children with one or two allergic parents were 1.86 and 2.91, respectively, compared with just 1.36 for those with no allergic parents.

C-section was linked to allergen sensitization as well, but only in children without allergic parents (OR = 2.14), the investigators found.

“Our results emphasize the importance of gene-environment interactions on the development of asthma in children,” the authors conclude. “The increased rate of cesarean section is partly due to maternal demand without medical reason. In this situation, the mother should be informed of the risk of asthma for her child, especially when the parents have a history of allergy or asthma.”

Reference:
Thorax 2009;64:107-113.