Severely premature babies: More survive being born early
More premature babies, born before 26 weeks, are surviving than ever before, according to a detailed analysis of the figures for England.
Severely premature babies were more likely to survive in 2006 than in 1995, the EPICure study found.
There was, however, no improvement before 24 weeks - which is the legal limit for abortion.
The figures, published in the British Medical Journal, also indicate the odds of severe disability have not changed.
Life can hang in the balance for children born prematurely, as their bodies are physically not ready for life outside of the womb.
The earlier they are born, the greater risk.
The EPICure studies, funded by the Medical Research Council, looked at premature babies born in hospitals throughout England in 1995 and 2006. Researchers expect the findings would apply equally across the UK.
Very premature babies
Very premature babies are not ready to survive in the world. And the earlier they are born, the worse the odds.
Even those that survive can remain in hospital beyond the point at which they would have been born had the pregnancy been full-term.
One issue is they can be incredibly small - sometimes able to fit in the palm of a hand. Their eyelids may still be fused shut.
Every part of their body is immature. This is noticeable in the skin which is very see-through. It is delicate and has not formed its waterproof layer.
The lungs are not fully developed, so breathing is a challenge and can require medical help. The gut is not prepared for food.
One of the greatest differences is in the brain. It has still not finished being wired up and looks smooth rather than folded.
The data for 2006 showed that 53% of babies born between 22 and 25 weeks and admitted to intensive care lived and were sent home. The figure for 1995 was 40%.
However, there was no improvement in survival at 22 and 23 weeks - which is before the abortion limit in England, Scotland and Wales.
Measures such as ensuring the newborn is kept warm and given steroids to help underdeveloped lungs are thought to have improved care.
However, the evidence shows that any benefits are largely confined to the first few days.
Researcher Prof Kate Costeloe, from Homerton University Hospital and Queen Mary, University of London, said: "Yes we do have increased survival of these babies, but that increase is all happening in the first week of life.
"It's very disappointing that they are not doing any better having survived the first week."
Prof Costeloe said the survival figures before 24 weeks were "terribly small". In 2006, of the 152 live births at 22 weeks, 19 were admitted to hospital and three survived.Long-term problems
A second report compared the health of the premature babies when they reached the age of three.
It showed 34% of babies admitted to neonatal care in 2006 were completely healthy, compared with 23% in 1995.
Prof Neil Marlow, from the Institute of Women's Health at University College London, said it was "encouraging" that more were surviving without disability.
Yet the odds of life-long disability such as cerebral palsy, blindness or being unable to walk, has not changed, at about one in five.
This combined with a large increase in admissions, from 666 in 1995 to 1,115 in 2006, means the number of people living with severe disability as a result of premature birth is increasing.
Prof Marlow said: "Because of the rise in the numbers of admissions, that actually means the numbers of children with disabilities in the population has gone up and that's really very important."'Life not possible'
There was a stark pattern in the 2006 survival statistics (up to the point a baby is discharged from hospital) based on how soon a baby was born.
- 22 weeks - 2% of 152 live births
- 23 weeks - 19% of 339 live births
- 24 weeks - 40% of 442 live births
- 25 weeks - 66% of 521 live births
- 26 weeks - 77% of 580 live births
Dr Simon Newell, a consultant in neonatal medicine at Leeds General Infirmary and vice-president of the Royal College of Paediatrics and Child Health, said: "We can only protect so much from the effects of immaturity.
"We are going very carefully from when life is not possible to when independent life is possible and protecting the brain through that journey."
He said these studies were "essential" when it came to difficult decisions about whether to pursue intensive care, or even to withdraw care.
He told the BBC: "It's not what we can do, but should we do it... without these sorts of data how would we know what to say to parents, what to do?"
Dr Alan Fenton, consultant neonatologist in Newcastle and from the British Association of Perinatal Medicine, said improvements in treatment had kept more people alive in the first few days, but new issues had emerged.
"In 1995 lung diseases killed you, but due to changes in the way we give care it is longer-term problems such as serious infections and gut problems," he said.
Andrew Whitelaw, a professor of neonatal medicine at the University of Bristol, said: "The average survivor was in hospital for over three months and this represents an investment of scores of thousands of pounds per baby.
"Having made this commitment it is clearly important that this is followed up by a smaller investment in support for the minority that have extra needs because of learning difficulties, visual impairment et cetera."