Baby's Gut Bacteria Determined by Breastfeeding and C-Section

A baby's gut microbiota may be influenced greatly by their moms, according to new research. Cesarean delivery and bottle feeding both affect exactly how much bacteria is in a baby's gut.

Published online in Canadian Medical Association Journal, the study examined the stool samples of 24 healthy, term infants in the population-based Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort. Six of the infants had been born by C-section and 10 were exclusively breastfed at sample collection at age four months. Using new culture-independent DNA sequencing, the researchers then examined what type of bacteria and how much were in each sample.

Surprisingly, the researchers found that breastfeeding and C-section actually determined the composition and amount of fecal bacteria. Infants born with C-section had significantly fewer bacteria of the Escherichia-Schigella and none at all of the Bacteroides species, regardless of breastfeeding. Those who had undergone elective cesarean had a particularly low bacterial diversity. Babies who were not breastfed, in contrast, had a higher prevalence of enteric and atopic disease-associated C. difficile.

In all, elective C-section was associated with the lowest richness and diversity of bacteria, and points to the fact that having a C-section may lead to health problems in children later in life.

Why is this the case? Passage through the birth canal gives babies a natural inoculation with bacteria from the mother. In addition, a mother's milk also shapes the baby's intestinal colonization; it's rich in prebiotics and selects for the persistence of beneficial bacteria and limits the colonization of harmful ones.

Exactly what this means for the babies, though, is unclear. Researchers are quick to point out that they're unsure whether it's more important to acquire a particular combination of specific types of bacteria, or if these factors are critical for healthy microbiota. However, previous research has shown that C-section and formula-fed infants have been associated with conditions such as allergies and asthma.