There is still a lot we do not know when it comes to the microbial composition of mom and baby during pregnancy. That being said, scientists have recently discovered that there are large changes that occur and various exposures that shape the infant’s microbiome. Whether it’s exposure to antibiotics, feeding, or delivery mode, these instances play a role in helping and harming the microbial development of the growing baby. Although only studied in rats, antibiotics taken during pregnancy have been shown to increase weight gain as well as significantly reduce bacterial diversity. This information and what we know about antibiotics, in general, are intriguing as the effects on immunity and the health of mom and baby come to light. On a more positive note, when babies can drink their mother’s milk, they are getting the optimal source of nutrition and are ingesting bacteria important in building a strong microbiome. Another important factor in microbiome development is the mode by which the baby is born. Although the microbial differences between a vaginal and cesarian birth only last for about 4-12 months, it’s important to note that vaginal delivery has shown to increase the diversity of bacterial species passed along to the baby. Whereas ceserian deliveries tend to cause delayed colonization of a few bacterial species and thus a lower alpha diversity is passed to the baby in this delivery mode. Although we know more now about pregnancy, birth, infancy, and how the microbiome is affected during these stages, there are still endless amounts to uncover.