Giving birth

Why vaginal seeding won't help babies born by C-section

The practice of smearing vaginal fluids on a baby just after birth might not solve the real problem behind Caesarean-born babies' imbalanced microbiomes.

Why vaginal seeding won't help babies born by C-section

Photo: iStockphoto

As researchers are learning more about the importance of a healthy microbiome for long-term health, parents are doing everything they can to give their infants a good, bacteria-filled start to life. For moms who have to undergo a Caesarean section, that sometimes means trying vaginal seeding—a practice that involves swabbing the mom’s vagina with gauze, and then smearing it all over the baby’s body and mouth just after delivery in the hopes of passing on healthy microbes. But a new study suggests the practice might not be all that effective—and it may even be dangerous.

In recent years, researchers have found that the gut microbiome can help to determine a child’s risk of everything from asthma to obesity. And many theories have posited that an infant’s trip through the birth canal is the first chance to populate his gut with healthy bacteria—in what some call a “bacteria baptism.” 

But the new study on vaginal seeding, which reviewed existing research and was published in the journal Frontiers in Medicine, suggests that while vaginally born and Caesarean-delivered babies do have very different microbiomes, this difference is likely due to antibiotics that are administered before a C-section, not vaginal bacteria. These antibiotics can cross the placenta to the baby, wiping out their microbes.

The study’s author, Lisa Stinson, a researcher in the Division of Obstetrics and Gynecology at the University of Western Australia, explains: "If passage through the vagina seeded babies with vaginal bacteria, we would expect to find these bacteria in babies born this way, but this is not the case. Microbes thrown out of balance in babies born by C-section are very similar to those thrown off balance in babies born to mothers receiving antibiotics but delivering vaginally. It is likely that routine antibiotic administration given to mothers delivering by C-section is a major underlying problem," explains Stinson.

Chelsea Elwood, an obstetrician and reproductive infectious diseases specialist in the Department of Obstetrics and Gynecology at the University of British Columbia, confirms that it is standard care for moms to receive an antibiotic before a C-section. “In fact, in the vast majority of abdominal surgery—regardless of whether it’s a C-section or a patient having a bowel removed—patients receive antibiotics prior to their operation to reduce the risk of surgical site infection,” she explains.

Elwood discourages the use of vaginal seeding because of the risks of introducing harmful viruses. “We have zero evidence that it’s beneficial and we have potential for harm,” she says. “Let’s say mom has a herpes outbreak that she doesn’t notice, then you take that virus and you put it directly in the baby’s throat. I don’t know how that viral inoculum may influence the baby in terms of developing, for example, herpes simplex virus meningitis.”

Elwood, who is currently studying the role that different modes of delivery have on an infant’s microbiome, says we actually don’t know for sure if or how delivery affects a child’s gut health. For example, even though it’s safe to assume that a baby who is born vaginally will be covered in vaginal bacteria, we don’t know that those bacteria actually colonize the gut where they can change health outcomes in the long term.

Most likely, there are many factors involved in establishing a healthy microbiome early in life. The study cites breastfeeding duration, maternal obesity and age at birth as a few things that could account for differences in babies’ guts. Elwood adds a child’s environment and the introduction of solids to that list of probable contributors.


For now, vaginal seeding is not recommended. But for moms who have C-sections, the good news is that how you deliver likely isn’t the only deciding factor that will affect your child’s microbiome. There will be plenty of other good opportunities to give them a healthy start along the way.

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