Do babies born by C-section have different microbiomes? Maybe not so much.

Scientists have long thought that the method of delivery has a big impact on the microbiome of a young child. On page 191 of Systematic, I wrote, “In fact, babies who are delivered by cesarian section have significantly different microbiome compositions from those who are delivered vaginally, though it seems that these differences usually disappear with time.” And while there was no good evidence linking the claimed differences to health outcomes later in life, the observation might have given some parents-to-be pause.

Recent evidence (paywall) from scientists at Baylor College of Medicine suggests that the claimed effect has been overblown: the researchers found some differences immediately after birth in the oral and skin microbial communities, but there was no change in the composition of the neonatal stool. By six weeks, even those slight initial differences had disappeared.

The upshot: don’t worry about the microbiome when picking a delivery method.