MUMBAI – Indian doctors have successfully removed "parasitic twins" or two foetuses that were growing inside the abdomen of a 20-day-old baby.

Called foetus in foetu, the condition is extremely rare, with fewer than 200 cases being reported worldwide until now, a handful of them from India.

The condition develops early in pregnancy where a malformed foetus is absorbed by the host twin. Though the foetus isn't alive, it continues to develop by absorbing nutrients from the host twin – hence the name "parasitic twin".

In this case, the woman was pregnant with triplets and two of the foetuses began to grow inside the abdomen of the baby.

"The surgery was challenging but the baby is healthy and doing well," Dr Anand Sinha, a paediatric surgeon who led the operation, told the BBC.

The infant was discharged from hospital a month back and there have been no complications so far, he added.

The doctor said the recovery period after the surgery is crucial, as infection or other complications could prove fatal for the child.

In 2024, a three-day old baby in Kolkata city died a day after he underwent surgery to remove two malformed foetuses from his abdomen.

In the latest case, the parents admitted their 20-day-old baby to Fortis Memorial Research Institute in Gurugram in July.

"She had a bloated abdomen, was irritable and unable to eat anything because the foetuses were squashing her stomach," Dr Anand said.

A scan showed two tumour-like shapes inside her abdomen, which were actually the malformed foetuses.

Dr Anand said surgery couldn't be performed immediately as the baby was dehydrated, malnourished and had to first be stabilised. Her condition improved after two days, and then a team of about 15 doctors performed the surgery.

"The operation took about two hours," Dr Anand said, adding that special equipment had to be used because of the baby's delicate, diminutive stature.

Also, since the foetuses were attached to organs like the liver, kidneys and the intestines, they had to be extracted with great care so that no organs or blood vessels were damaged.

"Throughout the surgery, the baby's temperature was monitored. We also had to make sure that there wasn't too much blood loss," Dr Anand said.

Foetus in foetu is often diagnosed during pregnancy, but Dr Anand says sometimes parasitic twins are found in adults if the condition goes undetected during infancy.

He says if not removed early on, the malformed foetuses continue growing in size as the person ages. And while these foetuses usually do not turn cancerous, they are likely to cause other problems to the individual, which will eventually lead to their detection.

In February, doctors removed two foetuses from the abdomen of a three-day-old baby in Maharashtra state. – BBC