Guatemalan twin 'very well' after surgery

LOS ANGELES, California (CNN) -- One of the Guatemalan twins who was separated from her sister in surgery this month is doing "very well" following an operation to repair skin grafts on her head, one of her doctors said Friday.

Thursday's operation, a reconstructive procedure, was the first for Maria de Jesus Quiej-Alvarez since the August 6 surgery to remove her from her conjoined sister, Maria Teresa.

Dr. Irwin Weiss, a pediatric intensive care specialist at UCLA's Mattel Children's Hospital, said Maria de Jesus is "back to herself."

"She's laughing, playing, very active, eating, and doing all the things that most one-year-olds do," Weiss told CNN's Connie Chung Tonight. "We think she says 'papa' and 'mama,' but we're not 100 percent sure. It sounds like it."

EXTRA INFORMATION Gallery: Separating the twins  Timeline: A look at conjoined twins throughout history

The girls remain in serious but stable condition, as they have for the past few weeks.

Doctors believe they've seen indications that Maria de Jesus is wondering where her formerly conjoined sister is, Weiss said. The one-year-olds were joined at the head for the first year of their lives until they were separated in a 22-hour surgery.

"She does seem to reach over her head and try to feel what was there," he said, adding doctors cannot know for sure what she is feeling for.

Weiss said Maria Teresa, who has had four operations including the separation procedure, has naturally had a more difficult time recovering than her sister. But she is now off a ventilator and breathing on her own.

"She's awake, but she's not as active and playful as her sister is," Weiss said. "But we kind of expect that for anyone who's had four major brain surgeries to be a little slower recovering. But if you look at her, she's better than she was last week, and we're optimistic that every week she'll improve."