The infant microbiome plays an essential role in human health and its assembly is determined by maternal– offspring exchanges of microbiota. This process is affected by several practices, including Cesarean section (C-section), perinatal antibiotics, and formula feeding, that have been linked to increased risks of metabolic and immune diseases. Here we review recent knowledge about the impacts on infant microbiome assembly, discuss preventive and restorative strategies to ameliorate the effects of these impacts, and highlight where research is needed to advance this field and improve the health of future generations.

Mammals have evolved to nourish their offspring exclusively with maternal milk for around half of the lactation period, a crucial developmental window. In view of oral-breast contact during lactation and the differences in oral microbiota between cesarean section (C-section) and vaginally delivered infants, we expected differences in milk composition by delivery mode. We performed a cross-sectional study of banked human milk and found changes related to time since delivery in bacterial abundance and glycosylation patterns only in milk from women who delivered vaginally. The results warrant further research into the effects of delivery mode on milk microbes, milk glycosylation, and postpartum infant development.