HealthDay News — A vaginal birth and breastfeeding make a notable difference in the bacterial composition of an infant’s gut, according to research published online in JAMA Pediatrics.

The research team tracked the birth and feeding records of 102 infants who were 6 weeks old. Roughly two-thirds of the infants in the study had been born vaginally, with the remaining third delivered via cesarean section. Similarly, about two-thirds had been exclusively fed breast milk in the first six weeks of life, while 26 were fed with a combination of breast milk and formula. Six infants were fed only formula.

Stool analyses revealed that an infant’s delivery method had at least as much of an impact on the gut differences as diet. The research team also found that infants fed a mix of formula and breast milk ended up with a gut composition at six weeks that was similar to that seen in infants fed formula alone, a finding not noted in prior investigations.

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“These results may inform feeding choices and shed light on the mechanisms behind the lifelong health consequences of delivery and infant feeding modalities,” the authors write.


1. Madan JC, Hoen AG, Lundgren SN, et al. Association of Cesarean Delivery and Formula Supplementation With the Intestinal Microbiome of 6-Week-Old Infants. JAMA Ped. 2016;doi:10.1001/jamapediatrics.2015.3732.