Doctors in Singapore may separate one-year-old Indonesian twin girls conjoined at the waist but are weighing whether the risks are too great.

Separating the girls would require elaborate and risky surgery, according to details of their case published in Singapore’s Straits Times newspaper on Thursday.

One girl has a hole in her heart. If she has a Heart attack in surgery, both would most likely die, the report said.

The intestines of the girls are joined and each would end up with just one leg because a third leg lacks a proper knee or hip joints, the report said.

“Our doctors are still evaluating whether it is feasible to separate the conjoined twins,” said a spokeswoman from Parkway Holdings Ltd., which owns Mount Elizabeth Hospital where the girls were tested after arriving from Indonesia last month.

The girls, born in rural poverty but sponsored by wealthy Indonesians after a local doctor refused to operate on them, have been moved to another Parkway hospital in Singapore, Gleneagles.

Specialists from Singapore’s KK Women’s and Children’s Hospital, also reviewed the twins at the request of Mount Elizabeth.

“Our surgeons concluded that it was technically possible to separate them,” a KK Hospital spokeswoman said. KK’s team considered the long-term implications such as whether the girls may eventually sit and walk, and if the family can cope with the long-term follow-up care, she added.

In 2003, Singapore’s Raffles Hospital conducted an unprecedented operation to separate Iranian adult conjoined twins, Ladan and Laleh Bijani, who were joined at the head. The marathon 52-hour surgery ended in their deaths.

That same year, the hospital performed a successful operation to separate South Korean twin baby girls joined at the spine.