Cooling the brain can minimise the risk of damage to babies deprived of oxygen at birth, research has confirmed.
The cap helped many babies
International tests of a special water cooled cap for babies' heads have produced highly promising results.
Babies fitted with the cap were less likely to die, or to be severely disabled. Cerebral palsy rates were cut by half.
However, the cap, developed by an international team of researchers, did not aid the most seriously injured.
A lack of oxygen at birth can result from a ruptured uterus, a placenta that peels off too early, or the rupture or collapse of the umbilical chord.
It is estimated that one in 1,000 babies in the UK are affected. The figure is much higher in the developing world.
Up to now, no intervention has seemed to make much difference - many babies die or develop problems such as cerebral palsy.
Researchers at University College London Hospitals (UCLH) discovered that damage to the brain does not occur immediately the organ is deprived of oxygen.
Instead, damage is the result of a cascade of chemical reactions, and there is a window of several hours before it becomes permanent.
Therefore, in theory it might be possible to intervene to block the chemical chain reaction and minimise permanent damage.
One way of doing this is to reduce brain temperature. Previous studies have shown that reducing the temperature by 3-4°C from normal seems to switch off many of the damaging reactions.
Why this is so is not understood, but it may be that cooling slows down chemical reactions, and gives the repair mechanisms found inside cells a chance to get to work without being overwhelmed.
The UCLH team joined forces with researchers in New Zealand, Bristol and Seattle to put theory into practice by developing a water cooled cap for babies' heads.
In total, 234 babies from around the world took part in the trial. Half received the cooling treatment, and half had standard intensive care.
The cooled babies received 72 hours of treatment followed by gradual rewarming and standard care.
Both groups were followed up for 18 months and assessed by paediatricians who were unaware which baby had been cooled and which had not.
The cooled babies showed significant benefits. There was a reduction in both the number of babies who died and in how severely disabled they were at 18 months of age.
However, the babies who had the most severe electrical deficits at birth - around 20% of the total - did not respond to cooling.
In the trial the treatment was given up to six hours from the moment of delivery, but there is evidence to suggest that the treatment may still be effective if given at a later stage.
The results suggest that for every six to eight babies suitable for treatment with the cooling cap, one will be saved from death or serious brain damage.
Professor John Wyatt, head of the UCLH team, said he was "encouraged" by the results.
"For the first time there is hope for babies who are profoundly at risk," he said.
The Medical Research Council is currently carrying out a major trial of the effect of whole baby cooling.
Professor Wyatt said that it was vital that the MRC trial was completed as it would be very important in helping to decide which approach was best.
He said there was still work to be done to determine the right temperature, and the right length of treatment before cooling was offered as a standard treatment.
He told BBC News Online that the theoretical advantage of brain cooling was to minimise possible side effects, such as circulation problems and increased risk of infection.
Simon Moore, of Action Medical Research, which helped fund the research along with the children's medical charity SPARKS, said: "This looks like really good news.
"By treatment immediately after birth, babies who are at risk will have a hugely increased chance of a life without severe disability."
Richard Parnell, head of research and public policy at the cerebral palsy charity Scope said the research was "interesting and exciting" but stressed more work was needed to determine the best way to use cooling to minimise risk.
The trial was sponsored by Olympic Medical in Seattle, which is now developing the cap for general medical use.