Better medical care is improving the survival chances of premature babies but failing to reduce the number suffering from lifelong health problems, according to new research.
Doctors studying extremely preterm babies - those born before the 26th week of pregnancy - warn "little progress has been made" in reducing serious long-term problems.
They say the children are a "significant public health issue" because of the increased workload for health, educational and social services.
Professor Neil Marlow, a neonatal care specialist at University College London Hospitals, told Sky News: "Intensive care for small babies is expensive, and providing care for children with disabilities as they grow up is also expensive.
"Although the number of babies in relation to the general population is relatively small, they have a very high need."
Researchers behind the long-running EPICure study compared premature babies born in 2006 with those born in 1995.
They found there had been a 44% increase in the number of extremely premature babies being admitted to neonatal intensive care, reflecting increasing optimism by doctors.
Survival increased from 40% to 53% over the decade, according to results published on bmj.com.
But in 1995, 41% left hospital with a major disability such as chronic lung disease, brain damage or serious eye problems, and there has been no improvement since.
In the Netherlands doctors do not attempt to save very premature babies - they argue that it causes more suffering, with little prospect of a successful outcome.
But Professor Andrew Shennan, medical advisor to Tommy's - a charity which funds research into premature birth, miscarriage and stillbirth - said doctors must do their best.
"Doctors who deal with these babies soon after birth have to make very careful decisions not to over-strive to maintain life at all costs. And I don't think that has changed.
"It is disappointing that disability remains a problem and isn't getting better and we need to look at why that is the case."
Nadia and Rosa Connelly were both premature. Nadia was 15 weeks early and her mum Sarah was told she had a 50% chance of survival. She says doctors were right to give her a chance.
"You don't know what is going to happen," she said.
"I was told she would have a severe mental or physical disability and she doesn't.
"So I dont think it is so clear cut. You can't say we are not going to treat this child."
UK charity Bliss , which provides support and care for premature babies and their families, welcomed the results of the EPICure 2 study.
Bliss chief executive Andy Cole told Sky News: “It is very welcome news that since 1995, 13 per cent more babies born at 24 and 25 weeks gestation have survived and that there has been an 11 per cent improvement in survival without disability.
"This progress recognises the huge skill and dedication of the nurses and doctors caring for these tiny babies and some notable improvements in treatment.
“This EPICure data emphasises the need for a range of community services to be available to support all premature babies after discharge and the increasing demand for follow up care by paediatricians and other specialists which is not yet being fully met.
“This research reinforces the crucial importance of continued investment to meet agreed national standards of neonatal care, to ensure the very best possible outcomes for these children.”