But, it cautioned, more evidence was needed of a genetic link before doctors warned mothers of a higher risk of breech delivery if their parents had also been born bottom-first.

• 但同时也警告说，对于父母为臀位分娩出生的人来说，医生在告知产妇具有臀位分娩高风险之前，应获得充分的证据支持。