How bacterial communities in the body influence human health
In the womb, a fetus enjoys the protection of a sterile environment. Only when the mother's amniotic sac ruptures before delivery does her baby face microbes for the first time. As he's squeezed through the birth canal, he picks up millions of bacteria from his mother. Most of the microbes are friendly and quickly take up residence on the baby's skin and in his gastrointestinal tract.