A gut feeling: bugs are critical for good health

While still in the womb, the gut of an infant is completely sterile. But as the birthing process begins, bacteria and other microbes soon start to colonize the surfaces of the infant’s body—the skin, nose, mouth, and by far the most densely colonized, the gut. Babies born by caesarean section are initially populated with different microbes (from the hospital and skin microbiota) than babies delivered vaginally (vaginal microbiota) (1, 2).