New research shows that despite improvements in neonatal intensive care, the most premature babies are no more likely to survive today than they were in the mid-1990s.
The report, which appears in the British Medical Journal, concludes that "the limits of viability for the survival of pre-term babies has been reached".
Between 1994 and 2005 not a single baby born after 22 weeks' gestation survived beyond discharge from hospital.
Of those born at 23 weeks, more than half were admitted to intensive care. Yet there has been no improvement in survival rates in the intervening years.
Only 18% of those babies survived long enough to go home.
One of the authors, Professor David Field from the University of Leicester, says: "You do get a sense with the most immature babies that they just can't respond to what we have to offer.
"It's almost as if we need something new, something extra, which at the moment we just don't have."
More encouraging is that more mature pre-term babies are more likely to survive now than they were 13 years ago.
Today, 41% babies born after 24 weeks' gestation - the current legal limit for abortions - survive beyond discharge.
In 1995 the figure was 24%. The study, which involved 16 hospitals with more than 55 000 births a year, nevertheless appears to undermine the argument that advances in neonatal medicine mean the legal limit for abortions should be lowered.
The time limit on abortions is due to be debated in the House of Commons in the next few days. But anti-abortionists say the weight of scientific evidence is now on their side.
21-year-old Danny Parrott from Coventry would certainly welcome a lower time limit on abortion. He was born ten weeks prematurely and has cerebral palsy.
But despite his disabilities he's a successful sportsman, and narrowly missed out on qualifying for the Beijing Paralympics.
"I've got friends who were about 18 weeks early, and they're doing fantastic things," says Danny. "One of my friends from school is training at university to be a brain surgeon."

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