PITTSBURGH -- Doctors in Pittsburgh have identified the 2-year-old conjoined twins they successfully separated in December.

The girls are doing well at Children's Hospital of Pittsburgh after the 24-hour Dec. 13 surgery.

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The hospital identified the mother as 26-year-old Catherine Nickson, of Cleveland.

"The twins are doing very well," said Dr. Joseph Losee. "They're happy and healthy and will be discharged soon."

Officials said the girls were conjoined from the breast bone to the groin. Among the many challenges facing the team was the fact that the twins shared a colon and had livers that were connected. They also shared a third leg.

"One of the doctors at the hospital they were born at, they actually came up with the idea of sending them here," said mother Catherine Nickson. "Soon as I got here, I met all of these people here, and I said, 'OK, they look like they know what they're doing.'"

The twins spent the majority of their first two years of life as patients at Children's Hospital, undergoing more than 10 procedures during the 18-month period of preparation, officials said.

The procedures included the placement of tissue expanders, which were used to stretch the skin to allow for reconstruction following the separation.

They likely will require further reconstructive procedures in the future, according to doctors.

"I think they're happy, because they can actually go to sleep without somebody punching them in the face," said Nickson. "So, I think they're happy to get away from each other."

The girls are the first conjoined twins to be separated at the Pittsburgh hospital. They are expected to spend time in another medical facility for a few months before they go home.