Exposing infants born by cesarean-section (C-section) to their mothers’ vaginal fluids at birth results in the development of a microbiota-the community of microorganisms that inhabit the human body-that is similar to those of vaginally delivered babies, finds a study published online this week in Nature Medicine. Delivery method is a major determinant of a newborn’s microbiota, but this pilot study demonstrates that vaginal microbes can be partially restored in babies delivered by C-section.
Microbes present in vaginal fluids colonize the skin, oral cavity and gut of babies as they are born; these microbes collectively form the microbiota. This early microbial exposure and colonization influences development of the immune system and impacts metabolism and immune function later in life. Babies born via C-section, which accounts for 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.
Maria Dominguez-Bello, Jose Clemente and colleagues report a procedure, termed vaginal microbial transfer, in which four infants were swabbed immediately after a C-section birth with gauze that had been incubated in the infant’s mother’s vagina for one hour prior to the C-section procedure. They then compared the babies’ microbiota to that of seven C-section-born infants not exposed to vaginal fluids and of seven infants born vaginally. They found that, 30 days after birth, C-section-born infants exposed to vaginal fluids had a microbiota that was more similar to that of vaginally born infants than to C-section-born infants 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. The authors did not investigate long-term clinical outcomes in these infants, and thus it remains unclear whether exposure to vaginal microbes has any durable effects on the makeup of the microbiota and/or the health of these babies.In an accompanying News & Views article, Alexander Khoruts writes 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.