A file photo of an operation in Saudi Arabia to separate conjoined twins
© AFP/HO/File LONDON (AFP) - Hope Williams, the smaller of the twins, died after being separated from her sister Faith, Great Ormond Street Hospital said. Her lungs were unable to support her breathing.
Professor Agostino Pierro, head of the surgical team, said Faith was in a "stable" condition, adding that the parents were "devastated by the loss of their daughter."
The mother of the baby girls, 18-year-old Laura Williams, is Britain's youngest-ever mother of conjoined twins. The pair were born by Caesarian section last Wednesday.
The sisters were joined from the breastbone to the top of the navel. They shared their blood circulation but had their own organs except the liver.
Doctors wanted to wait until the pair were older and stronger before attempting to separate them. Plans were brought forward to Tuesday, however, following concerns about their condition.
Pierro said surgeons had to operate because the twins' health was going "downhill."
"This was an emergency operation because there was a blockage in their joint intestine which could only be resolved through surgery," he said.
"The technical surgery worked well, although it was extremely challenging, and went according to plan."
More than 20 staff were involved and the twins were moved into different theatres after the separation, he said.
"However, very sadly, after separation baby Hope's lungs proved too small to support her breathing and she died last night in the presence of her parents.
"They are clearly devastated by the loss of their daughter and we offer them our deepest condolences on their loss.
"Baby Faith is stable after separation. She requires support for her breathing but she is gradually improving. However it is early days and complications can occur."
The twins weighed 10 pounds and eight ounces at birth.
Conjoined twins occur when the single egg from which identical twins develop fails to divide properly after conception.
It usually occurs in women aged 25 to 40 years old. The survival rate is between five and 25 percent.
Williams and her husband Aled, 28, from Shrewsbury, western England, were initially advised to terminate the pregnancy.
The teenager told The Mail on Sunday newspaper following the birth: "After I came round from the operation they wheeled me in to see them.
"They were both blowing bubbles. They were so beautiful. I couldn't stop looking at them.
"We knew that conjoined twins very rarely make it through the first 24 hours and we could see that one girl was a bit smaller than the other so we called the little one Hope and the bigger one Faith."
©AFP