Nearly two months after undergoing a transplant designed to infuse her body with healthy blood and defeat leukemia, a 13-month-old Simi Valley girl remains in isolation in a Los Angeles hospital.

Hailey Joy Kent, who received stem cells from a donor's umbilical cord on May 30, is still on a battery of medications as doctors monitor a blood count that fluctuates day to day. She's playing with her favorite rattles and seems mostly happy but faces a long list of challenges, like relearning how to eat.

"Considering what she's been through so far, she's doing all right," said Maria Kent, Hailey's mother, who all but lives at Childrens Hospital Los Angeles. "You just have to wait every step of the way. The threat of relapse is going to be there for a long time. You don't even know."

Maria and Rick Kent went through nine miscarriages before a surrogate carried the embryos that on June 6, 2006, produced Hailey Joy and her healthy twin brother, Ryan. The Kents also have an older daughter Heather, who is 21.

When she was 3 months old, Hailey was diagnosed with an unusual, aggressive disease called acute lymphoblastic leukemia.

Several months of chemotherapy didn't stop the disease. Hailey was admitted May 21 to Childrens Hospital. She was given a final, nearly lethal course of chemotherapy aimed at eradicating the diseased blood cells. The stem cells were then transplanted into Hailey to replace the bad cells with healthy blood.

The healthy cells are growing and now about 94 percent of Hailey's blood cells can be linked to the transplant, Maria Kent said, adding that the family hopes that medication triggers more cell growth and boosts that number to 100 percent.

The biggest fear is the leukemia will come back.

"Her (blood) counts go up and down," said Rick Kent, noting the pre-transplant chemotherapy meant she was fed intravenously. "Now the process is trying to get her to eat anything, which is a battle."

The Kents also worry about the risk of infection posed by Hailey's weakened immune system. But Dr. Neena Kapoor, director of the clinical bone marrow transplant program at Childrens Hospital, says she's encouraged because there is no sign of cancer and the new stem cells are producing healthy blood.

"Her nucleuses are growing beautifully," she said. "Right now, things are headed in the right direction."

Hailey is still in an isolated room but can be visited by family. She and twin Ryan have been together once since the transplant, celebrating their first birthday together at Hailey's hospital.

She takes steroids that can make her grumpy. But she smiles often and seems happy, though a little bored.

"She's in good spirits," said Rick Kent. "She's my hero. It's amazing everything that little girl has gone through."

Her family is trying to deal with the stress. Her mother spends as much time as possible at the hospital but still tries to get back to Simi Valley to see Ryan. Rick, a construction manager at Universal Studios Hollywood, said he manages by limiting his focus.

"The way I look at it is I'm going to get by today and I'm going to worry about tomorrow when tomorrow comes," he said.