A consultant treating a brain-damaged girl whose parents are fighting an order not to resuscitate told a High Court "she isn't suffering in any way".
Charlotte's parents say she has made "remarkable progress"
The doctor said 23-month-old Charlotte Wyatt "feels pleasure" and "has a tolerable quality of life now".
During the hearing her parents Darren and Debbie Wyatt's counsel argued last year's order "can no longer stand".
But the medic, referred to as Dr K, said he was "concerned" about treatment if she suffered a "major collapse".
Dr K said: "Charlotte has a tolerable quality of life now and I believe she feels pleasure.
"She has a good smile. That is significant.
"While all this is going on we are very pleased that she isn't suffering in any way. That's fantastic."
Giving evidence at the start of the two-day review of Charlotte Wyatt's case, her doctor added that it was "remarkable" that she had "beaten a 5% chance of survival".
Mr Justice Hedley was being urged by Darren, 33, and his wife Debbie, 24, heavily pregnant with the couple's fourth child, to discharge a "non-ventilation" declaration he made in October 2004.
The Wyatt's counsel, David Wolfe, told the judge that "the overwhelming medical consensus is that there are situations in which it would be appropriate to ventilate her if she needed it".
Mr Wolfe argued that the order should be rescinded.
"Debbie and Darren are content for the court to make a declaration that in the very unlikely event of her suffering a cardiac arrest it would be lawful for doctors not to ventilate her; but no wider than that," he said.
Mr Justice Hedley is also hearing medical evidence from experts called on behalf of Portsmouth Hospitals NHS Trust.
In August Mr and Mrs Wyatt, who are devout Christians, lost their attempt to persuade three Court of Appeal judges to overturn the order.
Charlotte, who was born three months prematurely in October 2003, was five inches long and weighed only 1lb (0.45kg).
Charlotte, who is two on 21 October, has serious brain, lung and kidney damage and has not yet left the hospital.
But according to her parents, Charlotte now smiles, reaches out to them and tries to talk - and they have spoken of their desire to bring her home.