Babies who are denied oxygen as they are being born have a high chance of suffering brain damage as a result.

BBC Correspondent Mark MacCallum: A simple but effective solution to the problem

Oxygen can be cut off during birth by a kink in the umbilical cord or a problem getting oxygen from the mother.

Oxygen starvation leads to brain cells committing suicide over the following three to four days.

Doctors say the new device means babies can avoid such damage by having their brains cooled.

At the moment the technique is on trial in New Zealand, but a large clinical trial is soon to start in the UK and US as well.

Chilling technique

The research features in the BBC's Tomorrow's World programme on Wednesday.

The New Zealand trial is being run by Dr Tania Gunn and Professor Peter Gluckmann at the National Women's Hospital in Auckland.

The principle is similar to that of applying ice to a sprain - doctors cool the brain from a normal temperature of around 37°C to 32°C.

Dr Gunn said: "There are dangers of hypothermia - anyone who's ever seen what happens to mountaineers who have been in the cold recognises that.

"But when it's done in a controlled situation with careful monitoring of the heart rate and the blood pressure and the oxygen levels, we've shown that it's safe in the levels we've taken it to."

Developing equipment

The team had to develop the technology themselves, as no such equipment previously existed.

They used an office drinking fountain connected to two plastic tubes. These bring the cooled water up from the pump in the fountain into the cooling cap itself.

Professor Gluckmann explained the approach.

He said: "We know that oxygen starvation starts a set of chemical processes in brain cells which leads them to commit suicide over 72 to 100 hours after they're starved of oxygen.

"What we discovered is that cooling stops those chemical processes.

"We don't exactly know which chemical process - so you can regard it in a sense as a bit miraculous - but it works."

Case studies

Tomorrow's World looks at two cases where the technique appears to have been successful.

One is the case of Thomas Wilkie, who had complications at birth. He wore the cap for 72 hours after he was born.

His father David said: "It was a pretty difficult time because he was born and it was obvious things weren't right.

"He wasn't screaming and moving - in fact he wasn't even breathing."

His parents feared the worst when tests soon after birth revealed he was at risk of brain damage.

Now, at 18 months, Thomas has just undergone his final developmental assessment. The doctors say he is growing up absolutely normally.

Fight for life

It also looks at the case of Cody Crump, who underwent a difficult delivery and was left fighting for his life.

Doctors said that if he did survive, he would be at risk of brain damage.

His parents agreed that doctors could try out the new technique on him.

After six weeks, he appears to be well.

Dr Gunn said: "If he hadn't been cooled he very easily may not have survived to be with us.

"He could well have had damage extending into these deep portions and involving a large area of the brain and that would mean he was brain damaged and would be badly handicapped later."