Background/Question/Methods The birth of a child may include routine use of antibiotics or a delivery by cesarean section.  We applaud these medical advances for their direct benefits.  However, birthing practices have been shown to disrupt the colonization of the microbial gut in newborns, which may have long term consequences on the development of a child’s immune system resulting in atopies (i.e., asthma, allergies, and eczema).  Animal models and other research have been used to demonstrate that not only the presence, but also the community composition of the gut microbiota, is essential for normal immune development.  Furthermore, it has been established that there are differences in the intestinal microbiota of children who have eczema, asthma, or allergies versus their non-atopic counterparts.  In utero an infant persists in an environment free of microorganisms.  During the birth process, as the baby moves down through the birth canal the baby encounters their first microbes and foreign substances stimulating the immune system of the mucosal surfaces.  Under normal conditions, where newborns are exposed to an abundance of the maternal microbiota, microbial colonization is dominated by bacteria with fast doubling times.  As bacterial numbers increase and resources are depleted, more specialized and complex communities become established.

Results/Conclusions Although the ultimate impact of how the microbial community establishes itself within an individual is still not well understood, there is evidence that this is a highly sensitive process.  Early differences in patterns of microbial colonization persist years suggesting colonization dynamics and assembly rules yield long-term differences.  Therefore, it is not surprising factors, such as the duration of vaginal delivery, birthing method (e.g., cesarean, vaginal), or even receipt of peripartum antibiotics affects microbial colonization of the newborn.  Consequently, it is important that we establish an understanding of the complexity of the microbial communities within the gut and how patterns of colonization based on possible disturbances may have both immediate and long term consequences.