Two heads, one body: what can be done for tragic twins?

So what does the future hold for a pair of conjoined twin girls, born with two heads and one body to farmers in south-western China last week?

They could grow up like American twins Abigail and Brittany Hensel, who celebrated their 21st birthdays this year after being born with the "extremely rare" condition - dicephalic parapagus - that the unnamed Chinese twins are thought to have.

And twins Krishna and Trishna, whose heads were joined, turned four this year after a 27-hour operation in Melbourne that involved 16 surgeons in November 2009.

Dr Susan Adams, director of surgery at Sydney Children's Hospital, Randwick, said separating the Chinese twins would be extremely complex if possible.

"You need a lot of detailed investigation to know what organs are shared and there are essential organs that you can't do without, like your heart and your lungs, your liver.

"And it really depends on which organs are shared in general terms with conjoined twins as to what the likelihood of survival of one or both of them and what the likely quality of life is."

She said with most conjoined twins, even if they are able to be separated, "there will almost always be some residual disability. It just depends on what the degree of disability is".

Abigail Hensel told the Daily Mail in 2006 that despite the difficulties and the attention they received, Brittany and her "never wish we were separated".

"Because we would never be able to do all the things that we do now ... like play softball, run and do sports."

And despite their physical closeness, the twins insisted they were two very different people.

"I'm more into like pink and girly and Brittany is more not into pink ... we take turns," Abigail said. "One day Brittany will pick the outfit and the next day I will pick the outfit."

Whatever happens, the twins, their parents and their doctors face a string of medical, ethical, emotional and psychological dilemmas, she says.

"It's a grim thing and a terrible ethical dilemma for the people looking after the twins and the family and a tragic situation."

The twins' parents would also have to contend with China's one-child policy, which restricts couples to having only one child.

But rural China expert Graeme Smith of the University of Technology, Sydney said the twins' parents would be able to negotiate with authorities about whether they could have more children.

"If your child passes away before a certain age, then you are allowed to try for another child," Dr Smith said.

"It would definitely be open to negotiation. The thing about the one-child policy is that it is a national policy but it's implemented in very different ways from province to province and even from county to county."

The sisters, who according to media reports are being examined by doctors at the Suining City Central Hospital in Sichuan province, have separate spines and esophaguses, but share other organs.

The girls' mother, who was not named by local paper the Huaxi Metropolis Daily, did not know she had twins until just two days before their birth.

She and her husband did not want to have the babies at first as they were afraid they could not afford to keep them alive, a nurse at the hospital told the Associated Press.

The babies weighed four kilograms and were 51 centimetres long when they were born, the Daily added.

One pair of conjoined twins are born for every 200,000 live births, the University of Maryland's medical centre said.