Around a quarter of babies in the UK and a third of those in the USA are now born by Caesarean section, many of which are elective. Maria Gloria Dominguez-Bello found that if babies are born through a cut in their mother’s abdomen, their starter microbes come from her skin and the hospital environment, instead of her vagina.24 It’s not clear what these differences mean in the long term, but just as an island’s first colonists influence the species that eventually settle upon it, the effects of a child’s first microbes could ripple through future communities. This might explain why C-section
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