Babies born by Cesarean section (C-section) are not always exposed to bacteria and other microbes present in the birth canals of their mothers—a factor that some studies have associated with health risks later in life. Now, researchers present preliminary data indicating that microbial communities could be at least partly restored by swabbing C-section–delivered babies with their mothers’ vaginal fluids immediately after birth.
Maria Dominguez-Bello et al (New York University) conducted a pilot study in which infants delivered by C-section were exposed to maternal vaginal fluids at birth. In the Feb 1 issue of Nature Medicine, they report in a Brief Communication that the gut, oral, and skin bacterial communities of these newborns during the first 30 days of life were similar to that of babies born by vaginal delivery, and enriched in bacteria that were underrepresented in unexposed C-section–delivered infants.
Although the long-term health consequences of restoring the microbiota of C-section–delivered infants are unclear, Dominguez-Bello et al conclude that vaginal microbes can be partially restored at birth to babies delivered by C-section.
Microbes from vaginal fluids colonize the skin, oral cavity, and gut of babies as they are born. This early microbial exposure and colonization influences development of the immune system and affects metabolism and immune function later in life. Babies born via C-section (more than 50% of total births in some countries) are not immediately exposed to these microbes and have a different microbiota at birth from those born vaginally.
In the vaginal microbiota transfer procedure of Dominguez-Bello et al, 4 infants were swabbed immediately after a C-section birth with gauze that had been incubated in the infant’s mother’s vagina for 1 hour prior to the C-section procedure.
The authors compared the babies’ microbiota with that of 7 infants born via C-section that had not been exposed to vaginal fluids and of 7 infants born vaginally.
Medscape explained that the researchers determined the composition of microbiota from infants and mothers using more than 1500 samples from anal, oral, and skin sites during the first month of life.
Dominguez-Bello et al found that, 30 days after birth, infants born via C-section and exposed to vaginal fluids had a microbiota that was more similar to that of infants born by vaginal delivery than to infants born by C-section and not exposed to vaginal fluids.
However, the authors also found that the vaginal microbial transfer was not complete and that the procedure did not transfer all of the microbes present in vaginally born infants.
In an accompanying News & Views article, Alexander Khoruts (University of Minnesota) says 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”. However, he highlights additional limitations, including the small sample size and the short duration of the study.
Although cesarean deliveries may be a medical necessity for 10% to 15% of births, almost 30% of infants in the United States are delivered by C-section.
Medscape explained that once infants are born, their body sites quickly become colonized by microbes from the mother and the environment. Dominguez-Bello et al found that at birth, neonatal bacterial diversity was highest in the anal and oral sites. Diversity in these areas decreased by day 3, whereas diversity in the skin increased with time.
Although the results of the current study are interesting, they are preliminary. “Labor is, of course, a very complex process,” explained senior author Jose C. Clemente at the press conference. “Our results establish feasibility, but not health outcomes,” he added.
It is unclear whether exposure to vaginal microbes has any durable effects on the makeup of the microbiota and/or the health of these babies.
“Of course, the mode of delivery is only 1 event that contributes to the development of microbiota in the first years of life. The background and clinical history of the mother, the choice for breastfeeding and its duration, and exposure to antibiotics are all critical determinants that will need to be carefully controlled in future investigations”, wrote Khoruts.
“Cesarean delivery, as well as other disruptors of early microbiota assembly, such as antibiotics and formula feeding, have been associated with later-life conditions including asthma, allergies, type 1 diabetes, and obesity,” Dominguez Bello told Reuters.
“The final and biggest and most important study, which is very expensive, is the one following babies for years,” explained Dominguez-Bello.
Reuters added that this intervention might carry an infection risk, and might not work for emergency C-section surgeries that leave no time to have women soak the gauze before babies arrive.
The Scientist added that women who volunteered for the intervention were likely to be “highly interested and motivated” to restore their newborn’s microbiota. Anita Kozyrskyj (University of Alberta, Canada) told The Scientist that unreported behavior—such as engaging in prolonged skin-to-skin contact after delivery—could itself promote differences in the infants’ microbial communities. “That’s the issue with having a report on such a small number—results could be skewed by 1 or 2 infants”, she explained.