There are many factors that can influence the colonization of an infant’s microbial community:
Bacteria in amniotic fluid: Before the infant is even born, bacteria can enter in the amniotic fluid, but currently it is still up for debate if there is a placental microbiome.
Antibiotic exposure: Antibiotics, just as for adults, disrupt the growth of microbial communities and thus cause dysbiosis. This can be caused by either the mother or the infant taking them.
Delivery and feeding modality: Infants who are born vaginally are exposed to the bacteria in the vaginal canal and varies significantly from those born from cesarean section. Some doctors recommend swabbing the vaginal canal and painting the cesarean-born infant with the bacteria it would have been in contact with if delivered vaginally. Furthermore, feeding by breastmilk or formula also varies the exposure to bacteria which colonize the infant.
Smoking: Smoking is known to reduce adult microbiota and mothers who smoke are also risking their infant’s as well. Studies have found that this can cause dysbiosis for the children later on in life, increasing the risk for obesity.
