Debbie Wyatt, 23, who is pregnant with her third child, rubbed her bump protectively at her council flat in Portsmouth. A few streets away, in St Mary’s Hospital, her 11-month-old daughter Charlotte lay in a cot, surrounded by teddy bears and medical tubes.

Born three months prematurely last October, Charlotte was so small that she fitted in the palm of her mother’s hand. She has serious heart problems and has been resuscitated three times.

Doctors believe that she is so sick that she should be allowed to die. They are seeking permission from the High Court not to put her on a ventilator the next time she stops breathing.

But Mrs Wyatt and her husband, Darren, 33, believe that their daughter has a chance of survival. They have vowed to fight the hospital all the way to the European Court of Human Rights.

“It has all been very difficult for us,” Mrs Wyatt told The Times as she prepared to travel to London for today’s hearing. “It has been so stressful, especially with me being pregnant again. I just hope the judge makes the right decision. We want to cling to any chance we have. We have to wait and hope.”

Mr Justice Hedley will today listen to expert medical evidence from both sides and he is expected to make a swift decision becauseCharlotte is so unwell. His ruling could set a precedent for future right-to-life cases.

Charlotte weighed 1lb (450g) and was 5in (12.7cm) long when she was born on October 21 at St Mary’s. She was given less than a 50 per cent chance of survival, but she pulled through the early months of life. She now weighs almost 12lb, the average weight of a three-month-old baby.

She has never left hospital; it was three months before her parents were able to hold her and five months before they could give her a bath.

Her vital organs are under-developed and she is fed by a tube because she is unable to suck from a bottle. Doctors say that she will spend the rest of her life in hospital.

She has almost died three times, but was taken to the paediatric intensive care unit and put on a ventilator, which has further damaged her lungs. The last emergency was a month ago, when doctors decided that her prognosis was so poor that, should her condition deteriorate again, she should not be resuscitated.

Mr and Mrs Wyatt try to visit Charlotte every day in St Mary’s, where she has her own room. They have hung a colourful mobile over her cot and on a shelf are pictures of Jesus, a cross and a china bowl with a prayer that reads: “Dear God, please bless me and look after me as I sleep.”

They say that, on a good day, she looks around, recognises them and even manages a smile. However, her two-year-old brother Daniel visits less often because the family GP believes that her condition could be to blame for his nightmares.

“We would feel we are killing our daughter if we let her go,” Mr Wyatt said. “We will go to the European Court if we have to.” Charlotte is Mr Wyatt’s fifth child: he has three children, aged 13, 12 and 8, from his first marriage and he and his wife moved from Birmingham to Portsmouth so that he could see his other family more often. Mrs Wyatt was a care worker in an old people’s home and her husband a trainee chef, but both have given up work because of stress.

The hospital said last night: “Portsmouth Hospitals NHS Trust’s sole motivation for going to the High Court has been our concern for the best interests of Charlotte Wyatt.

“The first duty of the Trust, its doctors, nurses and all staff is to the individual patient and to what is in the patient’s best interest. If, as in this instance, agreement cannot be reached between parents and clinicians, the trust is required to seek the views of the court.

“The Trust is grateful that Charlotte Wyatt’s parents through their barrister at court have made it clear that the care provided to Charlotte to date has been of the highest standard and they have no criticism of the way the hospital has treated their child.”

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