C-Section May Raise Child's Risk of Allergies, Asthma: Study

Natural delivery appears to expose babies to beneficial bacteria, researchers say.

MONDAY, Feb. 25 (HealthDay News) -- Babies born by cesarean section are more likely than others to develop allergies, a new study says.

Researchers evaluated more than 1,200 newborns when they were 1 month, 6 months, 1 year and 2 years old.

By age 2, babies born by cesarean section were five times more likely to have allergies than those born naturally when exposed to high levels of common household allergens such as pet dander and dust mites.

The findings "further advance the hygiene hypothesis that early childhood exposure to microorganisms affects the immune system's development and onset of allergies," study lead author Christine Cole Johnson, chairwoman of the health sciences department at Henry Ford Hospital in Detroit, said in a hospital news release. "We believe a baby's exposure to bacteria in the birth canal is a major influencer on their immune system."

Babies born by C-section have a pattern of "at-risk" microorganisms in their gastrointestinal tract that may make them more susceptible to developing the antibody immunoglobulin E (IgE) when exposed to allergens, Johnson said.

IgE is linked to the development of allergies and asthma.

The study was scheduled for presentation Sunday at the annual meeting of the American Academy of Allergy, Asthma and Immunology in San Antonio, Texas.

The study found an association between cesarean birth and allergy risk, but it did not prove cause-and-effect.

Data and conclusions presented at medical meetings are considered preliminary until published in a peer-reviewed journal.

More information

The American Academy of Pediatrics has more about allergies and asthma in children.