When they go through the birth canal, they get exposed to the entire bacteria population of their mother's vaginal and GI microbiomes.

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One might conclude that this trait evolved to ease their passage through a narrow birth canal, but it seems to result from the way vertebrate skeletons develop.

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In addition, young mothers face terrible threats to their health such as fistula -- a hole in the birth canal caused by prolonged labor without prompt medical intervention.

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When they performed 30 mock deliveries, using three-dimensional models of the mother's pelvis and a baby, the team found turning the baby so its spine faces the mother's belly was the safest way to proceed if the baby's shoulders were stuck in the birth canal.

BBC: NEWS | Health | Tricky birth delivery aid created