Surgeons at Stanford University's Lucile Packard Children's Hospital successfully separated 2-year-old conjoined twins in a complex, nearly 10-hour operation Tuesday.

The surgery took slightly longer than anticipated, but doctors said they anticipate Angelina and Angelica Sabuco, who were joined at the chest and abdomen, will recover fully.

"The long-term prognosis is that we would expect a happy, healthy set of girls. We don't see any barriers to a complete recovery," the lead surgeon, Dr. Gary Hartman, said after the surgery was completed.

The surgery began at 6:30 a.m., and the twins were separated shortly after noon. The remaining hours of the surgery involved reconstructing the girls' chest walls, abdominal muscles and skin where they had been connected.

The girls had what is called a "thoraco-omphalopagus" connection. Their livers, diaphragms, breast bones, chest and abdominal muscles were fused, but they had separate hearts, kidneys, stomachs and intestines.

Hartman had said he considered severing the liver to be the riskiest part of the procedure because of the possibility of severe blood loss, but that went smoothly. "We were able to close the abdominal muscles without a graft, and the chest closure also went better than we anticipated," Hartman said.

This is the second separation of conjoined twins to be performed at Packard Children's. In 2007, a set of twins from Costa Rica was successfully separated by a team led by Hartman. The Sabucos' surgery was Hartman's sixth separation.

The surgery involved about 20 physicians and 15 to 20 operating room staff.

The girls' parents, Ginady and Fidel Sabuco, did not know the twins were conjoined until Ginady Sabuco was seven months pregnant.

"I thank God for everything. Words cannot express how the family feels for the successful separation of our twins," said Ginady Sabuco, 33. The twins were born in the Philippines, but moved to San Jose with their mother to join their father. The couple also has a 10-year-old son. The family has health insurance.

The girls are expected to remain in the hospital for two to three weeks.