Researchers at the UCSD School of Medicine and Icahn School of Medicine at Mount Sinai determined that the microbial composition of a baby delivered by cesarean section can be altered to more closely match the microbiome of a vaginally-delivered baby. The research was published by Nature Medicine last Monday and suggests that transferring the mother’s vaginal microbes can help the development of babies’ immune systems.

Co-author and Programmer Analyst Antonio Gonzalez Pena at UCSD explained that various human body sites — such as oral, skin, vaginal and fecal — have different bacterial communities that are affected when a baby is delivered vaginally or by cesarean section. Previous research linked the differences with future health problems.

“Epidemiological studies have reported associations between C-section delivery and an increased risk of obesity, asthma, allergies and immune deficiencies,” Gonzalez Pena told the UCSD Guardian. “Thus, the question was: can we restore the vaginal community in C-section-delivered babies?”

The researchers collected samples from 18 infants and their mothers, consisting of seven born vaginally and 11 delivered by scheduled C-section. Of the latter sample, four were exposed to their mothers’ vaginal fluids at birth. To do so, sterile gauze was incubated in the mothers’ vaginas for one hour before the C-section, and within two minutes of delivery, the babies were swabbed with the gauze.

Over the next month, researchers collected a total of 1,519 anal, oral and skin samples from the mothers and infants. The team then used a gene-sequencing technique to identify the types and relative quantities of bacterial species present at each body site.

According to the study, vaginally delivered infants host bacterial communities similar to those of the maternal vagina, whereas C-section-delivered babies are fortified in skin microbiota, which is a specific type of microbe. The microbiome that colonizes the body of newborns can influence the development of the immune system, and early interaction with commensal, or symbiotic, microbes is essential for healthy immune development and metabolic programming.

After one day, the microbiomes of babies that were delivered vaginally or by C-section with exposure to vaginal fluids were more similar to the maternal vaginal microbiomes than to those of C-section-delivered infants that were not swabbed. The outcome was consistent after 30 days, though the microbiome similarities in oral and skin samples were greater than the anal samples. Gonzalez Pena elaborated on the feasibility of normalizing infants’ microbiomes and the consequential health benefits.

“These results show that it’s possible to inoculate C-section babies with vaginal microbes, the “normal” newborn microbiome, which might help the development of a healthy immune system,” he told the Guardian.

According to the study, one in two births are delivered by C-section in some countries, while only 15 percent of births are estimated to require the surgery for the protection of the mother’s or baby’s health. The Huffington Post suggests that C-section rates may depend on hospital policies, the threat of malpractice and cultural norms. As reported by the National Partnership for Women & Families, the U.S. cesarean birth rate increased from 4.5 percent in 1965 to 32.2 percent in 2014.

Director of the Center for Microbiome Innovation at UCSD Rob Knight led the study and related his research to an experiment of his own after the birth of his daughter.

“Not so much as scientists but as parents, we took matters into our own hands and gave her the microbes she would have naturally been born with had everything gone according to plan,” Knight told The San Diego Union-Tribune.

Knight, who is also a professor of pediatrics, computer science, and engineering, clarified that his daughter is now four years old and healthy, but that one uncontrolled experiment is not enough evidence from a scientific perspective.

“The present work is a pilot study — we need substantially more children and a longer follow-up period to connect the procedure to health effects,” Knight told the Times of San Diego.

According to Gonzalez Pena, future work could include determining the long-term effects of inoculation for the microbiome and the immune system, improving inoculation methods and understanding if the results can be attributed to a single part, several parts, or the entirety of the bacterial community.