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Delivery Mode and Diet Affect Infant Gut Microbiome

By Tim Dean

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In a recent Dartmouth-led study published in JAMA Pediatrics, researchers showed that the way infants are delivered and fed can affect the variety of bacteria, or microbiome, in their intestines at six weeks of age.

In one of the largest studies of the factors that determine infant gut microbiome composition, researchers examined relationships between the intestinal microbiome of 102 healthy infants and both delivery mode (vaginal vs. cesarean section) and feeding method (breast milk vs. formula), including supplementation of breast milk with formula.

The study yielded some interesting and novel results—both delivery mode and feeding were independently associated with microbiome composition, with delivery mode as strongly linked as feeding, even six weeks after birth.

The study was also the first to look at the impact of combination feeding on microbiome composition. "Surprisingly, babies that were fed both formula and breast milk had microbiomes that more closely resembled those of babies that were fed exclusively formula," says Anne G. Hoen, PhD, a study co-author and an assistant professor of epidemiology and of biomedical data science at Geisel. And breast-fed infants had microbiomes that were distinct from either combination-fed or formula-fed babies.

"Understanding the patterns of microbial colonization of the intestinal tract of healthy infants is critical," says neonatologist Juliette Madan, MD, MS, a co-author of the study and an associate professor of medicine (pediatrics) at Geisel, "not only for determining the health impacts of specific and alterable early life risk factors and exposures, but also the potential consequences for both short-term and long-term health."