A huge study of babies' stool samples has found key differences between infants born vaginally and via Cesarean section, offering clues about the development of the human immune system, researchers said on Wednesday.
Vaginally born babies got most of their gut bacteria from their mother, but C-section babies did not and had more bacteria linked to the hospital around them, the study found.
It is not clear what impact the difference may have on children's future health, and the findings should not deter women from having C-section births, the scientists leading the work said.