ROCHESTER, MINN. ? After Mayo Clinic surgeons took nearly seven hours to untangle their livers, reposition their hearts and divide a shared intestine, 5-month-old twins born joined at the chest and abdomen were sleeping in separate beds Friday.

“We expect them to have a smooth night, but they are critically ill, and we expect them to stay that way for the next 24 to 48 hours,” said Dr. Christopher Moir, the lead surgeon.

Abbigail and Isabelle Carlsen spent their first five months looking eye to eye, often bumping legs and arms and touching each other in the face.

That changed at 4:28 p.m. when the last tissue connecting the girls was cut, said Mayo Clinic spokesman Lee Aase.

“If any of you looked outside today, you noticed it was cloudy and rainy and the sun was nowhere to be seen,” said the girls’ father, Jesse Carlsen. “I think that’s because it was in that operating room, with our girls and this team. And today all of our prayers have been answered, and I can’t thank you enough for helping our girls.”

Jesse Carlsen, left, gives one of his conjoined twin daughters a kiss as he and wife Amy Carlsen, right, of Fargo, N.D., wait in a hallway to enter surgery with the girls in Rochester, Minn., Friday, May 12, 2006. The infants, Abbigail and Isabelle Carlsen, who were born in November, were to undergo separation surgery at the Mayo Clininc.

The girls’ livers were intertwined and they also were joined at the diaphragm and the pancreas, and shared part of an intestine.

Doctors also removed both of the girls’ gall bladders during the procedure, so the drainage systems in the organs could be rerouted, Aase said.

Aase said that after the girls’ livers were separated, the medical team applauded, having completed one of the more complicated parts of the operation. The liver separation was difficult because of the way the organs were fused and because the circulatory structures inside the livers needed to be divided correctly.

Doctors said the surgery was complicated but there was a 90 percent to 95 percent chance that both girls would survive.