Baby's first gut bacteria from mothers mouth?

Until recently, it was thought that babies are born with a sterile gut and that they pick up microbes on their journey through their mother’s vagina which migrate to colonise the gut.

Additional microbes are collected over the first years of life. In a study at the University of Houston, USA researchers took samples from inside the placentas of 320 women after they had given birth and sequenced the DNA of bacteria present and found that the bacterial species were most similar to those found in the adult mouth rather than to those in the vagina or gut. The team also found that different amounts of some of the bacterial species in women who had given birth prematurely before 37 weeks of pregnancy compared with the typical profile of those who went to full term. It is thought that bacteria from the mouth are carried by the blood stream to the placenta (Aagard K. Ma J. et alia Science Transl. Med.237ra. 2014 DOI;10.1126/ scitranslmed.3008599).