Formerly Conjoined Twins Doing Very Well

Formerly conjoined twins have ''excellent'' chances of survival after a grueling separation surgery, and one of the toddlers is even breathing on her own, doctors said Friday.

Two-year-olds Yurelia and Fiorella Rocha-Arias of San Jose, Costa Rica, were conjoined at the chest and abdomen and shared an oversize liver until Monday, when doctors in Palo Alto separated them during a 9-hour surgery.

Fiorella _ who has always been slightly larger and stronger than Yurelia _ was taken off her ventilator Wednesday and has been breathing on her own for two days.

''We are very happy with the outcome so far,'' said lead surgeon Dr. Gary Hartman of Lucile Packard Children's Hospital. ''These are two very strong little girls.''

Although Yurelia is still on a ventilator and heavily sedated, the twins' cardiovascular intensive care physician said chances for survival are higher than the 50-50 odds doctors gave them earlier this week.

''Current chances for survival are excellent,'' said Dr. Gail Wright, who would not provide a specific odds for survival.

On Wednesday, surgeon Dr. Frank Hanley performed a six-hour surgery on Yurelia to correct a life-threatening congenital heart defect that prevented enough oxygen from getting to her tissue. Doctors then reconstructed her chest wall.

The girls' parents, Maria and Jose Luis Rocha-Arias, have requested privacy and declined to comment.

The girls arrived in San Francisco on July 25 and received weekly injections of sterile saltwater into balloons placed under their skin. The procedure stretched their skin to compensate for the holes surgeons cut into their abdomens.

Packard doctors are donating their time to treat Yurelia and Fiorella, who have nine older siblings. Mending Kids International, a faith-based nonprofit based in Santa Clarita that helps sick children, arranged transportation and housing.