There are many factors that could affect and influence the colonization and health of microbial communities in infants. In the review article Nuriel-Ohayon et al. 2016 factors such as modes of delivery, feeding, weaning and antibiotics were investigated to determine if and how they affect microbial health in infants. During pregnancy a mother goes through many physiological changes, including alteration in the endocrine, immune and metabolic systems. With these physiological changes comes changes in the microbiomes in the gut, vagina, placenta and oral cavity. Changes in these microbiomes may be a factor in microbiome formation in newborns. However, it is still unclear if colonization and formation of the microbiomes in the fetus starts during or after pregnancy. Different methods of birth, cesarean vs. vaginal, have varying effects on bacterial compositions and formation in newborns. Cesarean section births have been correlated with increased cases of celiacs disease, asthma and obesity, which could be caused by differences in microbiomes. Breastfeeding has been shown to transfer microbes from the mother to the newborn and has a profound effect on the formation of the microbiome when compared to formula feeding. Overall, there is a lot of research that still needs to be done to understand the full effects of how the microbiomes form and their effects on newborns health.
