Formerly conjoined 2-year-old twin girls walked, played and swatted at bubbles Tuesday during their first public appearance since risky November separation surgery, which doctors said they had only a 50 percent chance of surviving.

"I feel very happy and very content, because my girls were born anew in this hospital," said Maria Elizabeth Arias, the toddlers' mother, speaking through a translator.

Dr. Gary Hartman, who led the surgery at Lucile Packard Children's Hospital at Stanford University, said the girls would likely face few complications when they return home to Costa Rica, where they were born joined at the chest and abdomen.

The twins — Yurelia and Fiorella Rocha-Arias — were also connected at the right atria of their hearts, the chamber that receives blood from the rest of the body, and they shared a liver and some blood.

"The girls are doing well. They have healed. They have had all of the procedures that we think they're going to need to have," Hartman said. The pair are ready to return home as soon as travel arrangements are made, he said.

After being separated from her sister, Yurelia required complex heart surgery to correct deformities that made her turn blue when excited or upset while still conjoined, doctors said.

Yurelia's heart started to function normally following the operation, said Dr. Frank Hanley, who performed the heart operation. The smaller of the two, she has flourished since the operation, doctors said.

The girls arrived in San Francisco on July 25 to begin preparations for the surgery.

Packard doctors donated their time to treat the twins, who have nine older siblings. Mending Kids International, a faith-based nonprofit based in Santa Clarita, California, that helps sick children, arranged transportation and housing. Hartman estimated the cost of the surgeries and treatment — which directly involved as many as 300 people — at $2 million.