TORONTO - A feisty and complex baby girl at the centre of a heart donor drama has defied her doctor's prognosis by surviving off life-support and will choose her fate on her own terms, her father said Wednesday.

The parents of Kaylee Wallace had come to terms with her seemingly imminent death when they agreed to remove her respirator Tuesday with the intention of seeing her heart go to another critically ill baby.

The two-month-old child suffers from a rare brain condition, Joubert syndrome, and it was believed the severity of her case would cause her to stop breathing without a respirator when she sleeps.

Not only did Kaylee not fall asleep during the window of opportunity to perform the transplant, she continued breathing on her own through the night and into Wednesday.

"Kaylee's a very complex little girl who is going to make her decision on her terms and nobody else's," Jason Wallace said outside The Hospital for Sick Children.

"If the terms are to pass away, we just want to make sure everything is done right for the organ to be saved. If not, we want our daughter to go home."

However, Kaylee's condition worsened Wednesday night and she stopped breathing several times during the evening, news station CP24 reported.

The child that was to receive the heart, one-month-old Lillian O'Connor, suffers from truncus arteriosus, which means her heart can't get enough oxygen to her body.

Lillian's parents, Melanie Bernard and Kevin O'Connor of Stratford, P.E.I., said Wednesday their daughter has "weeks to months" to live. Outside the hospital before going in to "kiss our daughter good morning," O'Connor called Lillian a "fighter."

The child remained at the top of the transplant list and as soon as a heart is available, a transplant was to proceed, the hospital said.

Wallace and Kaylee's mother, Crystal Vitelli, of Bradford, Ont., said Tuesday that the idea of having their girl's heart live on in another baby was the only comfort they had after being told their child would die.

The girl also has severe kidney problems.

"As parents we've decided that what we'll do is take it by the moment," Wallace said after meeting with doctors Wednesday.

"We're prepared if she's going to go home disabled in any way shape or form we would be happy with that outcome."

Dr. Micheil Innes, a clinical geneticist at Alberta Children's Hospital, said while he doesn't know the particulars of Kaylee's case, the severity of apnea - periods in which they don't breathe - varies widely in children with Joubert.

He said about 75 per cent of cases will have some apneas in their early childhood.

"I think it would be the minority of children that have such severe apnea that they would die of their condition, but some children are that severely affected," said Innes.

"For some of the children with Joubert, maybe some of the more mildly affected children, they have this breathing problem when they're younger and they do seem to outgrow it."

A parent of a teenage daughter with Joubert syndrome called the condition an "emotional roller-coaster."

"As Erin grew up there were definitely times where we weren't sure what the next week was going to bring or what milestones she wasn't going to be able to obtain," Karen Tompkins, who is also a Canadian representative of the Joubert Syndrome Foundation, said from Windsor, Ont.

The syndrome is characterized by a missing part of the brain that connects information between the brain and the body, so those messages get mislaid, Tompkins said.

"Anything that's (related to motor functions) is compromised: walking, talking, swallowing, grasping and breathing," she said.

There is a wide spectrum of ability with those who have Joubert syndrome, Tompkins said, and added in some people the brain can "reroute information" as they get older.

"My daughter, who is almost 16, has been able to reroute the information and she walks and talks and very rarely stops breathing," she said.

"She's in school. She has developmental delays, but she's reading and doing simple math."

Tompkins said the foundation knows of just 500 families in the world affected by Joubert syndrome.

- With files from Allison Jones