Urgent action is needed, say researchers, as the number of low-birthweight babies rises to one in 14

A record one in 14 babies in the UK - about 49,000 a year - are born underweight or premature, new research shows. The number of low-birthweight babies has increased by more than 10 per cent in a decade, the study says, and they now make up the biggest proportion of births since records began in the 1950s. The UK is also at the top of a western European low-birthweight baby league.

The new study will prompt a debate into the costs of looking after premature babies as they grow up and the future burden on the NHS.

Researchers revealed social class differences were a factor, with the most low-weight babies born to single mothers and manual worker families.

While much research has focused on childhood obesity, and the trend to larger birth-weights, the report by specialists from the Institute of Child Health and the London School of Hygiene and Tropical Medicine shows the proportion of low-weight babies - under 2.5kg (5.5lbs) - has risen rapidly.

The reasons for this include improvements in neonatal care resulting in more low-weight babies surviving than previously, a rise in the number of teenage and older mothers, and increases in the use of fertility treatments, such as IVF. Research suggests that IVF babies are more than twice as likely to have a low birthweight.

Low birthweightscan lead to health problems either immediately, in childhood or later in life. Sixty-two per cent of infant deaths in 1999 were babies under 2.5kg.

Low-weight infants are also more likely to be shorter, have increased blood pressure, suffer diabetes, and have higher rates of heart disease, stroke and lung disorders.

Last week, Lord Winston, professor of fertility studies at Imperial College London, outlined the potential risks for test-tube and low-birthweight babies. His comments prompted a national debate about IVF and the research into its long-term effects.

For the most recent study, published in Journal of Epidemiology and Community Health, researchers reviewed data on births in England and Wales going back to 1993.

Researchers say urgent action is needed to tackle the problems, and warn of the impact on the demand for future health services.

Bliss, the premature baby charity, says advances in technology are among the reasons for the increase. They point out that two decades ago, 20 per cent of babies weighing less than 1kg at birth survived, compared to 80 per cent today.

Ruth Powys of Bliss said: "Our concern is the strain this puts on the service. Mothers are being transferred all over the country because of cot and staff shortages. Adequate funding should be set aside for the sophisticated equipment and treatments needed to keep these babies alive. In addition, the social issues that cause mature motherhood and teenage pregnancies need to be tackled."

Additional reporting by Sarah Weaver

Born too soon

* Premature birth is defined as birth before 37 weeks of pregnancy.

* About 49,000 births, out of 700,000 in the UK each year, are premature.

* About 130 premature babies are born each day in the UK.

* The average weight for premature babies is 2lb. The normal range is 5.5lbs-7.7lbs.

* The UK's lightest baby, Aaliyah Hart, born in Birmingham in May, weighed just 12oz.

* Alex Franks, born in 1999 at 22 weeks, and weighing just 1lb 1oz, is thought to be the most premature baby to survive in the UK.

* 50 per cent of premature babies suffer health problems.

'Trinity's still small, but she is healthy'

Trinity Dinter is a little miracle. She was born nine weeks premature and weighed less than 4lbs. Science kept her alive; she spent the first seven weeks of her life in hospital.

She needed hi-tech assistance to aid her breathing, and a feeding tube into her stomach because she was not old enough to process food normally. Five months on, Trinity, the first child for Justine and Marc, is, at 13lbs 11 oz, still underweight for her age.

"There was no reason for her being born prematurely as far as they could tell. It could be down to stress, genetics or an infection,'' said Justine, 31, who gave birth at Queen Charlotte's hospital in London.

"Although she didn't need resuscitation, she had to have oxygen to help with her breathing and a system which keeps her lungs inflated.

"I don't know whether she would have survived without modern technology. They said that without help she would have had to spend a lot of energy breathing, but I don't know whether than meant she would have died without the technology. One thing we do know is that it certainly helped.

"Although she is a healthy baby now, the future does worry me. She may be at higher risk of health problems in later life because she was so small. You just don't know what is going to happen in the years to come. There is an increased instance of hyperactivity, learning difficulties and other things.

"It seems that whatever you are going through with a new baby, the fact the baby was premature and a low weight puts a slant on almost everything.

"Trinity is 13lbs 11oz now, but that is small for her age. At five months, she is still in clothes meant for a three-month-old. She is small, but the main thing is she is healthy.''