Doctors have called for urgent action to improve intensive care facilities for newborn babies.
Thousands of babies need intensive care when they are born
They say staff shortages and a lack of specialist cots are putting some infants at risk.
They have warned that the situation could get worse when new rules on how long junior doctors can work each week come into effect in August.
Health Minister Stephen Ladyman said the government was spending millions of pounds improving services.
Thousands of babies born in the UK each year require intensive care to help them survive their first few hours and days.
However, high demand means many expectant mothers and newborn babies need to be transferred to other hospitals, sometimes hundreds of miles away.
Earlier this month, 40-year-old Lesley Mullins revealed how she had to be flown from Surrey to Birmingham after going into premature labour at 29 weeks.
She was forced to make the 100 mile trip after finding there was no place for her at Frimley Park Hospital near her home.
A study by doctors in Yorkshire, published in this week's Archives of Disease in Childhood suggests staff shortages and a lack of cots are to blame.
Doctors at Leeds General Infirmary examined how many newborn babies were transferred to intensive care units at other hospitals over a six-month period in 2000.
They found that there had been 800 transfers during this time. Almost half of these involved women who were about to give birth. The vast majority were urgent cases.
The doctors found that almost half of these transfers occurred because of a lack of cots or staff.
They said the figures revealed "an unacceptable volume" of transfers between hospitals and said the situation was probably similar in other parts of the country.
"We doubt that the situation nationally is very much different," they wrote.
Another study by doctors in Oxford, published last year, reported similar findings.
The Liberal Democrats say a lack of intensive care cots is to blame for the high number of transfers.
Party officials say the number of cots has fallen by 20% since 1997. Their figures are based on information given to MPs by the Department of Health.
In an accompanying editorial in the journal, one of the country's leading experts Dr Luc Cornette, who is also based at Leeds General Infirmary, calls for a major review of how neonatal intensive care is organised.
He recommends the creation of a new national body to oversee services and to set guidelines on how and when women or infants are transferred to other hospitals.
Dr Cornette also calls for nurses to be given more responsibility for looking after these infants, as currently happens in north America.
He said this could help overcome problems when new rules on junior doctors' hours are introduced.
"New working patterns need to be considered," he said.
Mr Ladyman, said the government was committed to improving intensive care for newborn babies.
"In April 2003, we announced an extra £70m over three years to improve the provision of care for very sick and premature newborn babies.
"This money will provide up to an additional 75 neonatal intensive care cots and other specialist equipment."
He added: "The NHS is working hard to put in place systems to ensure that such moves happen as quickly as possible, are planned and is the shortest possible distance from a patient's home."
But Shadow Health Secretary Andrew Lansley warned the situation could get worse.
"We fear that the current staff shortages are set to worsen.
"Experts have warned that a third of the workforce are set to take retirement in three years and staffing pressures will increase when the European Working Time Directive comes into force in August 2004."