In recent years, there has been an increase in the number of babies born by caesarian section (C-section), especially in developed countries such as the US and UK. The rate of pediatric allergies and asthma has also been rising, leading some to wonder if there might be a connection between the way babies are delivered and the development of allergies and asthma during childhood.
With vaginal deliveries, babies are exposed to their mother’s microflora (friendly bacteria) in the birth canal. This exposure affects the composition of the baby’s intestinal microflora, which plays a role in the developing immune system. Some theorize that birth by c-section affects a baby’s developing immune system, making them more susceptible to develop allergies and allergic diseases. Research into the connection has been inconsistent. Some studies find a definite link while others don’t. In today’s post, we’ll summarize some of the research available on the topic.
o A 2005 study from Oregon Health & Science University found an increased risk of being diagnosed with allergic rhinoconjunctivitis (AR) among children born by c-section. They also found an increased risk of asthma, specifically in girls born by c-section.
o A Mayo Clinic study published the same year found no association between delivery by c-section and the subsequent risk for developing childhood asthma.
o A 2008 study out of Children’s Hospital of Boston found a link between c-section and atopy and allergic rhinitis among children who have a family history of allergies and asthma.
o A 2008 study out of Denmark found that c-sections are associated with a moderate risk increase for allergic rhinitis, asthma, hospitalization for asthma, and possibly food allergy, but not for inhalant atopy or atopic dermatitis.
o A 2009 Norwegian study found no link between c-section and the development of food allergies in children during the first 2 years of life.
o A 2012 study of Greek children found that delivery by c-section is associated with asthma and atopic sensitization in childhood. Family history of allergic disease did not seem to influence the connection between c-section and asthma; however, the connection between c-section and atopy is stronger when there is a family history of allergies.
This year, researchers from Henry Ford Hospital presented their findings at the 2013 Annual Meeting of the American Academy of Allergy, Asthma & Immunology in San Antonio. They found that children born by c-section are 5 times more likely to develop allergies when they are exposed to high levels of common indoor allergens. They also found that in comparison to children born vaginally, children born by c-section are more likely to be sensitized to at least 1 food, when the mother has a history of allergies. “We believe a baby’s exposure to bacteria in the birth canal is a major influencer on their immune system”, said Christine Cole Johnson, PhD, MPH, chair of the department of health sciences at Henry Ford Hospital.
It’s important to note that none of the above studies show that c-sections actually cause the development of allergies and allergic diseases, but some do suggest an association. This information may give clinicians some clues as to how allergies develop and provide insight for how they might be prevented or treated in the future.
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6. Younus M. Abstract #82. Presented at: 2013 Annual Meeting of the AAAAI; Feb. 22-26, 2013; San Antonio.
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