Surgeons in Australia have begun a complex operation to separate Bhutanese conjoined twins.
The 15-month-old girls, Nima and Dawa Pelden, are joined at the torso and share a liver and possibly a bowel, doctors say.
They were brought to Melbourne with their mother to have surgery in October, but it was postponed so the girls could improve their nutrition.
Doctors said they were confident the twins were now ready for the operation.
About 18 specialists in two teams, one for each girl, are taking part in the procedure at Melbourne’s Royal Children’s Hospital. The surgery is expected to last at least six hours.
Conjoined twins are very rare – it is thought one in every 200,000 births – and around 40-60% of these births are delivered stillborn.
Only a few separations are carried out around the world each year.
Nima and Dawa face each other, and cannot sit down together. They can stand if they do so at the same time.
“What we will be looking for is simply what bits actually connect the two girls together,” lead surgeon Dr Joe Crameri told reporters on Friday.
Dr Crameri said they would separate the liver, but one “unknown” was whether the girls shared a bowel.
If so it would also be divided, he said, and “our challenge will be to reconstruct their abdominal walls to close it over”.
The girls and their mother, Bhumchu Zangmo, 38, were brought to Australia from Bhutan by Children First Foundation, an Australian-based charity.
Elizabeth Lodge, from the charity, said Ms Zangmo was feeling “a little bit scared” about the procedure, but had shown “extraordinary calmness” so far.
Ms Zangmo would spend the day praying and meditating, she added.
The state of Victoria has offered to cover the A$350,000 (£195,000; $255,000) cost of the operation.
The family is expected to return to the Himalayan kingdom, one of the world’s poorest nations, after the procedure.
In 2009, the same hospital performed a successful operation to separate Bangladeshi conjoined twins.
The girls, Trishna and Krishna, who were joined at the head, underwent a life-saving 32-hour operation.