Breastfeeding and formula may influence infant microbiome more than vaginal birth, flags study

10 Apr 2023 --- Mothers’ vaginal microbiome composition does not significantly affect that of their babies’, according to new research from the University of British Columbia.

NutritionInsight sits down with Maria Rodriguez-Palmero, medical director at AB-Biotics, who sees it as no surprise that breastmilk plays a critical role in infant gut flora.

The study of more than 600 women concluded that regardless of birth mode and exposure to the maternal microbiome, mothers’ vaginal microbiome composition does not predict the composition of babies’ stool microbiome at ten days or three months after birth.

Maternal vaginal swabs were collected prior to delivery, and stool samples from the babies were collected within 72 hours of delivery, as well as at ten days and three months after birth.

Although the researchers did find statistically significant differences in microbiome composition by mode of delivery – vaginal vs. C-section – differences were primarily attributed to antibiotic exposure around the time of birth. 

“Other maternal sources like breast milk and exposure to the environment likely play a much larger role in establishing gut flora than previously believed,” says Scott Dos Santos, a Ph.D. candidate at the University of Saskatchewan and first author of the study.

The study found that breastfeeding and infant formula would likely influence the infant gut microbiome more than the birthing method.The Magic of milk
Infant formulas containing human milk oligosaccharides (HMOs) or probiotics are gaining in popularity, as they aim to give the baby what regular infant formulas are missing.

“A lot of evidence points out that breastmilk – which could be considered a symbiotic since it contains good bacteria – has a big impact on babies’ gut microbiota composition. In turn, it benefits the development of the immune function and other aspects of health, both in the short and the long term.” 

“We expect to keep seeing exponential growth in these types of products, and we hope that education around the subject also grows since it’s important for parents to be able to identify high-quality infant formulas enriched with clinically tested probiotics or other ingredients,” she says.

One of the study’s co-authors, UBC Ph.D. student Zahra Pakzad, is conducting further work to analyze the breast milk microbiome and better understand its relationship with infants’ gut microbiome.

“We had the opportunity to have conversations with hundreds of our participants on their postpartum experiences with breastfeeding and formula feeding, which further motivated us to understand the breast milk microbiome,” said Pakzad. 

“If we find this microbiome to be a significant contributor to infant gut microbiome development, this could help with the development of better infant probiotics and formulas.”

Establishing the microbiome 
The study states that when babies are born, their gut is a nearly sterile environment. But that quickly changes as the infant’s digestive tract becomes home to trillions of microbial cells throughout their early development.

This gut microbiome is an important part of overall health, and alterations early in life have been associated with negative health outcomes later on, including asthma and obesity.

It has long been assumed that birth mode and exposure of newborns to their mother’s vaginal microbiome during delivery greatly affects the development of a baby’s gut microbiome. This has given rise to practices like vaginal seeding, which aim to expose babies born via C-section to their mother’s vaginal microbiome.Infant probiotics and specialized HMOs have been shown to positively influence the infant microbiome.

However, these latest findings, published in Frontiers in Cellular and Infection Microbiology, suggest there is no longer a rationale for vaginal seeding as a practice, says Dr. Deborah Money, a professor of obstetrics and gynecology at UBC and the study’s senior author.

Rodriguez-Palmero argues that the study’s results might have been limited by sticking to just the mother’s vaginal microbiome.

“The study concludes that maternal vaginal microbiome composition at delivery does not affect infant stool microbiome composition at ten days and at three months. However, this investigation did not take into account the impact of maternal stool microbiota or perianal microbiota, among other factors.”  

More to explore?
Rodriguez-Palmero points out that there are still many research questions open and a lot to investigate in this field. 

“For example, in the same study, investigators found that antibiotic use before giving birth does affect babies’ gut microbiota development, although the process is not very well understood, and we do not know whether this effect is mediated by an alteration of mother’s gut microbiota which is transferred to the infant.”

Infant stool microbiomes did show some differences in composition by delivery mode (vaginal or C-section) at ten days postpartum, although this effect was vastly reduced by three months.

“In a period of early and rapid development, we still have to investigate whether a difference in microbiota composition over this period of time may have an impact on the development of the baby, particularly in the immune system development.”

The study is part of the Maternal Microbiome Legacy Project, a collaboration between researchers at UBC, the University of Saskatchewan, and the Women’s Health Research Institute at BC Women’s Hospital and Health Centre.

By Missy Green