A British hospital says that a conjoined twin has died after surgery to separate her from her sister.

Great Ormond Street Hospital said Wednesday that Hope Williams died Tuesday night after the surgery. The hospital says her sister, Faith, is in stable condition.

The twins were born last week, joined at the abdomen, to 18-year-old Laura Williams.

Twins who share an abdomen usually share the liver, bile ducts from the liver, and parts of the intestines.

At least 40 doctors, nurses and other health professionals were involved in the separation of the Williams twins in London.