Lactation period – Breast milk contains bacteria that will colonize in the infant’s gut. Also contains maternal milk factors that affect bacterial growth and metabolism such as human milk oligosaccharides, secretory IgA, and anti-microbial factors.
Weaning period and the introduction of solid foods – Solid foods introduce a variety of bacteria and will diversify their microbiome.
The delivery mode of the infant – Vaginal versus cesarean births influences the infant’s initial exposure to microbial communities.
Breast milk or formula feedings – Breast milk provides antibodies that help the infant fight illness while the formula may provide the infant with a larger quantity of minerals and key nutrients impacting the gut microbiome.
Maternal diet, health, treatment before and during pregnancy – Maternal body composition, nutritional stores, and diet determine nutrient availability for the fetus. Fatigue has been reported to influence the production of breast milk.
Maternal use of antibiotics – Antibiotics can influence breast milk and in turn, the infant’s gut microbiota by modifying gut defenses and may have dose-related effects on the infant.
Infant environment – From delivery, place of residence, to who cares for the infant impact availability to nutrients and microbial communities.
