A two-year-old boy from Huaxi, has undergone an operation to give 'birth' after doctors diagnosed him as 'pregnant'.

Xiao Feng, was brought to hospital after his stomach had become so distended that he had begun to suffer breathing difficulties.

Once admitted, doctors took x-rays and MRI scans and discovered that Feng was carrying the undeveloped foteus of his own twin inside his stomach and they rushed him to surgery.

The removed foetus measured 20 cm in width and had a fully formed spine and limbs, including fingers and toes.

The parasitic twin would have developed into a boy and had grown so large that almost 2/3rds of his affected twin's stomach was taken up.

Identical twins form when an egg splits in half after fertilization.

But conjoined twins or foetus-in-foetu siblings occur when the egg fails to fully separate.

Dr Jonathan Fanaroff, a neonatologist at Rainbow Babies and Children’s Hospital in Cleveland, said some conjoined twins can survive as 'parasites', but not when one twin absorbs the other.