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How to boost a baby's "good bacteria" after C-section birth

Babies born by C-section aren't exposed to the same mix of beneficial bacteria at birth.

Kati Molin

At the moment babies emerge into the world, a host of beneficial bacteria begins to colonize in their gastrointestinal tract. Research shows that this bacteria plays an important role in the development of the immune system. It is part of the microbiome, the bacteria living in our bodies that research suggests is essential to maintaining human health in any number of ways.

Exposure to these bacteria is interrupted with C-section birth, however, because instead of traveling through the birth canal where they would come into contact with their mother's bacteria and incorporate it into their own developing microbiome, cesarean babies are taken directly from the uterus. Almost a third of U.S. babies are delivered by C-section.

While cesarean delivery is often necessary to ensure the health and safety of both mother and child, it can have a lasting impact on aspects of a child's health. C-section delivery been associated with an increased risk of asthma, allergies, obesity and immune deficiencies later in life.

Now researchers are looking to give C-section babies the microbes they're missing -- and hopefully some of the health benefits -- by swabbing babies born via C-section with their mother's vaginal fluid shortly after birth.

Dr. Maria Gloria Dominguez-Bello, an associate professor in the Human Microbiome Program at the NYU School of Medicine, and Dr. Jose Clemente, an assistant professor in the Department of Genetics and Genomic Sciences and the Immunology Institute at the Icahn School of Medicine at Mount Sinai, and colleagues collected microbiota samples from 18 infants and their mothers; seven of the babies were born vaginally and 11 were delivered by scheduled C-section. Within minutes of birth, four of the infants born via C-section were swabbed with gauze that had been in the mother's vagina for one hour prior to delivery.

DNA analysis of more than 1,500 samples from infants and mothers at six times during the first month of life revealed that the microbiomes of babies who were swabbed after cesarean birth were similar to those of babies born vaginally.

Bacteria colonized quickly on a number of body sites and changed during the first month. C-section delivered babies who were not exposed to vaginal fluid had microbiomes that more closely resembled the bacterial DNA of human skin.

In another published study, Dominguez-Bello and colleagues showed that dust found in hospital operating rooms, especially places that aren't cleaned as often -- on top of the surgery lamp, the walls, the grids of AC vents -- contains human skin cells, which could all contribute to skin bacteria on C-section babies.

"The origin of the human skin bacteria is probably a lot of people -- the cleaning team, doctors, nurses," Dominguez-Bello told reporters at a press briefing. "We would think that the mother is less important as a contributor. Also, she is below the baby [during a C-section] so gravity acts against that."

Researchers noted that the findings, reported in Nature Medicine, are only preliminary. The number of babies tested was very small, and long-term clinical outcomes have not yet been investigated, so it remains unclear whether exposure to vaginal microbes would have any lasting effects.

It is also important to note that all of the test participants were screened prior to the study to ensure that the mothers were not carrying any potentially harmful bacteria such as group B Streptococcus (GBS) or vaginosis. "Mothers had to go through a number of tests to make sure it is a safe procedure," Clemente told reporters. "The take-home message would be don't do this at home."

In an accompanying News & Views article, Dr. Alexander Khoruts of the University of Minnesota said that the authors "have taken an important first step toward developing active interventions that may someday enhance the introduction of the newborn to microbial partners and facilitate a life-long healthy symbiotic relationship."