A Salt Lake girl and her mother, the recipient and donor in the first live-donor lung transplant in the nation, were doing well and both breathing on their own at Stanford Medical Center in San Francisco Saturday night.

A lobe from the mother's right lung was removed Thursday and implanted by surgeons to replace the 12-year-old girl's right lung, damaged by a respirator she was placed on after her premature birth more than a decade ago.The identities of the girl and her mother, 48, have not been released at the family's request.

"The latest information we have is that they are both very stable, they are both breathing on their own," said medical center spokeswoman Diana Diamond.

"They both remain in intensive care, but the mother was breathing on her own shortly after the operation and the girl was breathing on her own by (Friday) morning," Diamond said.

"We expect the mother will be released sooner than the daughter because of the nature of the two operations. They're both expected to do very well. The girl's lung is expected to grow to normal size," Diamond said.

The girl's condition, called bronchopulmonary dysplasia, causes scarring and high pressure in the lung, impairing her breathing. Doctors had given the girl 12 to 18 months to live before the transplant.

The transplant procedure took about four hours, according to surgeons. A parent-child transplant was done because of a close tissue match between the two, which surgeons hope will lessen the possibility of the child rejecting the lung.

Dr. Vaughn Starnes, head of Stanford's heart-lung transplant program, said the mother and daughter matched on four of six genetic markers, or tissue antigens, compared to two matchups used in transplants from non-related, brain-dead donors.

Fourteen children have received heart-lung transplants in Stanford's program but half have suffered from rejection severe enough to impair the function of the transplanted lung, according to Starnes.

The rejection rate of children in the Stanford program is twice that of adults, which the surgeon said could be attributable to a more active immune system.

Using tissue from a close relative, with a higher number of genetic marker matchups, could enhance the recipient's acceptance of the donated lung, he said.