NEW YORK (Reuters Health) – Among children who have a parent with allergies or asthma, delivery Caesarean section appears to increase the odds that they will develop allergic rhinitis and atopy – but not asthma – US researchers report. The investigators note that to the best of our knowledge, this is the first study to look at the "relationship between birth by Caesarean section and atopy and allergic diseases at school age among children at high risk for atopy," Dr. Juan C. Celedon, from Harvard Medical School in Boston, and colleagues note in the Journal of Allergy and Clinical Immunology. The study involved 432 children who were followed from birth to nine years of age. One or both parents had a history of allergies or asthma. Physician-diagnosed asthma and allergic rhinitis in the children was assessed using caregiver interviews conducted at least twice a year. Allergy skin testing was performed in 271 children at an average age of 7.4 years.

Children born by Caesarean section were 2.1-times more likely to develop atopy than their peers born by vaginal delivery, the report indicates.

Similarly, the authors found that Caesarean section increased the risk of allergic rhinitis 1.8-fold. As noted, however, Caesarean section did not increase the risk of asthma or wheeze. Celedon and colleagues speculate that the lack of exposure to maternal vaginal and faecal flora during Caesarean section and the absence of labour could both have indirect immunologic effects that promote atopy.