Transmission of bacteria through breast milk

Microbiote lait maternelle

Breastfeeding fundamentally shapes a child’s intestinal microbiota. Previous studies had indicated the presence of many bacteria in breast milk, as well as differences between the intestinal floras of breastfed and non-breastfed children.


This time, an American group literally traced the bacteria’s transfer from the mother to the child. Researchers analyzed the bacterial composition of breast milk, the mother’s areola skin, and the intestinal flora of breastfed newborns in 107 mother-child pairs (0 to 2 years) in good health. The results show that while the microbiota in each of these three sources—breast milk, areola, and child’s stool—are distinct, there is a real dose-dependent transfer from the mother to the child based on the proportion (whether it is exclusive or not) and duration of breastfeeding. A child receiving at least 75% of its total milk intake from breast milk in the first month of life receives 27.7% of the bacteria present in breast milk on average, and 10.3% of those from the areola. Although the child’s intestinal microbiota changes considerably after the introduction of solid food, this transfer continues, attesting to the lasting impact of breastfeeding on its composition.

This result is especially relevant considering that breastfeeding is associated with a reduced risk for a number of diseases: allergies, diabetes, obesity, and chronic inflammatory diseases.


Pannaraj PS et al. Association Between Breast Milk Bacterial Communities and Establishment and Development of the Infant Gut Microbiome. JAMA Pediatr. 2017 May 8. doi: 10.1001/jamapediatrics.2017.0378