The Vaginal Advantage

Study finds that a "normal" birth coats a baby with beneficial bacteria.

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Babies born vaginally have a decreased risk of certain immune system disorders, including asthma and allergies, compared with those born by Cesarean section, according to recent studies. Researchers now think they know why. Entering the world via the vagina exposes babies to several kinds of beneficial bacteria, including Lactobacillus; these normally comprise more than 95 percent of vaginal bacteria and go on to colonize the newborn's intestine.

C-section babies arrive coated with varieties of bacteria commonly found on adult skin, especially the Staphylococcus species. Most of these bacteria come from the mom's skin, but they may also be transferred from others in the delivery room, including the dad.

The type of bacteria on newborns' skin seems to influence the development of their digestive and immune systems, says study co-author Maria Gloria Dominguez-Bello, Ph.D., of the University of Puerto Rico.

More research is needed on how to boost immunity in C-section infants, but breastfeeding could be a big help, she says. "It makes biological sense because both the birth canal and breastfeeding are natural ways to inoculate the baby."

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