Considering the complexities involved in growing a little human being, it’s actually surprising that developmental slip-ups, such as this, don’t happen more often.

But when a baby in the US was born with a second mouth, the “extremely rare” duplication joined only a handful of similar cases in medical history.

First picked up as a right mandibular mass on prenatal ultrasound, during the mother’s third trimester, doctors initially considered a broad differential diagnosis, including a cyst, teratoma and fibrous dysplasia.

However, once born, it was clear the baby girl had a duplicate oral cavity and mandible — complete with lip, teeth and even a small tongue that moved in synchronisation with the main tongue as she fed — a craniofacial duplication known as diprosopus or ‘two faced’.