A baby born through the vaginal canal picks up critical microbes along the way that help it stay healthy later in life. But babies delivered via cesarean section miss out on those useful, gut-colonizing bacteria, which may put them at greater risk of developing certain health conditions and developmental disorders.
Now, researchers at Southern Medical University say that by exposing C-section babies to the microbes they’ve missed—an intervention called vaginal seeding—doctors can partially restore these missing gut bacteria. The procedure may even aid in their early development. Newborns delivered via C-section who received their mother’s vaginal microbes had more advanced motor and communication skills than other C-section babies months later, the team reports today in Cell Host & Microbe. But some clinicians argue these benefits for infants have not yet been proved, nor has the procedure’s safety.
“This study establishes a link showing that there is a possible benefit in a select group of infants and mothers,” says Mehreen Zaigham, an obstetrician at Lund University who was not involved in the study. “But it has to be proven with larger longitudinal studies.”
The microbiomes of C-section babies look a lot different from those of babies born vaginally. In particular, they have lower numbers of Lactobacillus, Escherichia, and Bacteroides bacteria in their guts. These microbes are believed to be critical for growth and are thought to help protect against asthma, allergies, obesity, and autoimmune disorders—all conditions that are more common among C-section babies. A few highly controversial studies have suggested some babies delivered by C-section may be at a greater risk of developing neurodevelopmental conditions such as autism spectrum disorder, which some researchers attribute to their disrupted microbiome. Other researchers have roundly criticized that suggestion, however.
To restore the microbiomes of infants delivered by C-section, researchers have come up with a simple solution: Swab them with bacteria from their mother’s vagina shortly after they are born. This method, called vaginal seeding, was first clinically tested 7 years ago by Jose Clemente, a geneticist at the Icahn School of Medicine at Mount Sinai, and Maria Gloria Dominguez Bello, a microbial ecologist at Rutgers University, who found the procedure indeed restored microbes that C-section babies lacked. However, these results were based on a small group of just 11 babies.
In the new paper, Clemente and colleagues tested this method with a larger group of 68 C-section babies. Shortly after delivery, a nurse swabbed each baby’s mouth and body with a gauze soaked either in saline or in the mother’s vaginal fluid. (To avoid the possibility of inadvertently transmitting disease, the researchers excluded any women with sexually transmitted infections.) Six weeks later, researchers took samples of the babies’ poop and studied their fecal microbes. They found that infants who had received their mother’s vaginal microbes had increased levels of gut bacteria, particularly of Lactobacillus. Overall, their microbiomes looked more like those of vaginally delivered infants than those of the other C-section babies swabbed with the saline-soaked gauze.
When the babies reached 3 months and 6 months old, their parents reported via questionnaire that those who had undergone vaginal seeding were slightly more advanced in their motor and communication skills than those who had not.
Wayne Cutfield, a pediatric endocrinologist at the University of Auckland who was not involved with the study, cautions that this apparent developmental effect is subtle, and that the scores of both groups fell within the normal range. Additionally, the questionnaire is normally used to assess whether children are below a certain cutoff and developmentally impaired—not to measure typical development milestones. “It’s a bit of a misuse of the tool,” says Deborah Money, a researcher and obstetrician gynecologist at the University of British Columbia who was not involved with the study. Measures administered by clinicians would be more convincing, Dominguez Bello adds.
The study’s sample size also remains too small to make firm conclusions about any benefits associated with vaginal seeding, Money argues. In previous work, she found that a giving a baby its mother’s vaginal microbes did not influence its gut bacteria in more than 600 cases. Other studies have suggested factors such as breastfeeding influence a baby’s gut microbiome more than the route of delivery. Money argues that pumping more effort into studying vaginal seeding unnecessarily spreads fear about negative health outcomes associated with C-sections. For the most part, she says, the microbiomes of C-section babies and vaginally delivered babies looks the same later on in life. “We need to stop the panic about this,” she says.
Some experts also worry that vaginal seeding could pass on infections to a baby. “It could potentially be dangerous for the for the infant without adequate screening of the mother for pathogens,” Cutfield says. (The American College of Obstetricians and Gynecologists does not recommend vaginal seeding outside of clinical trials.)
Clemente says more research into vaginal seeding will help scientists pin down the specific microbes that babies need to encounter in their earliest hours and days to give them the best chance at healthy development. Doctors could then expose newborns to just this particular combination of bacteria, rather than a microbial scattershot. “We all want to move [on] from inoculating a baby with a mixture of very different things,” he says.
