Separated twin undergoes reconstructive surgery

Both girls are in serious but stable condition after being separated almost a month ago.

LOS ANGELES, California (CNN) -- One of the Guatemalan twins surgically separated from her sister earlier this month underwent a two-hour reconstruction operation Thursday to repair skin grafts on her head, doctors said.

Doctors said the surgery was a planned procedure for Maria de Jesus Quiej-Alvarez.

"Everything went well," said Irwin Weiss, a pediatric intensive care specialist at UCLA's Mattel Children's Hospital. "They went in and made things a little bit better. Took some areas that were not looking as well, fixed them, made them look better."

Maria de Jesus continues to show better progress than her sister Maria Teresa since the separation operation.

"She laughs, she smiles, she giggles, she eats, she takes a bottle, she eats regular food," Weiss said. "She's very active, as one would expect from a 1-year-old child."

Both girls remain in serious but stable condition.

Weiss said Maria Teresa, who has had several surgeries in recent weeks to relieve a blood clot, is now off a ventilator and breathing on her own.

"She's awake, she does open her eyes," he said. "We're also seeing that every day she is making a little more progress."

The 1-year-old twins, born conjoined at the head, were separated during a 22-hour operation August 6.