Hospital units for premature and sick babies are being stretched to the limit, a new report out today suggests.
Staff shortages together with units being forced to work at maximum occupancy is affecting the way care is delivered, the charity Bliss said.
Babies are also being sent on long journeys due to a lack of cots in their local unit.
According to the latest report, staff shortages remain a "huge problem" across the UK.
Between 2006 and 2007, 160 more nurses were recruited to neonatal units but there still remains a shortfall of 1,700 nurses, it said.
The British Association of Perinatal Medicine laid down standards in 2001 saying one neonatal nurse should be assigned just one baby to look after in intensive care.
In high dependency care, the ratio should be one nurse to two babies and, in special care, one nurse to four babies.
The latest report analysed responses from 194 of the 213 hospitals with a neonatal unit in the UK, looking at their activity between April 1 2007 and September 1 2007.
It found that only one in five met all of the standards set down by the British Association of Perinatal Medicine.
In addition, one intensive care and 25 high dependency units reported having no dedicated neonatal consultant last year.
All specialist baby units are supposed to keep occupancy levels at no more than 70% on average in order to be able to cope with urgent admissions.
But the latest report shows that just one in five intensive care units met this standard, while a third of all units reached 100% capacity or more at some point.
One in five units were forced to close for seven weeks and seven units closed to new admissions for more than seven months over the same period.
The Bliss data, which was obtained under the Freedom of Information Act, also found that more than half of units had to close to new admissions at some point.
Over the five-month period, almost 500 babies were transferred between units due to a lack of staffed cots - an average of three babies a day.
Transfers are sometimes necessary for medical reasons but Bliss said they should not occur due to low staff numbers or not enough cots.
In 2007, around 82,000 babies needed to be admitted to hospital for neonatal care - around one in 10 (11%) of all births.
On average, a baby is admitted to neonatal care every six minutes.
Andy Cole, chief executive of Bliss, said: "Doctors and nurses provide amazing care to hundreds of premature and sick babies and their families every day.
"However, professionals are increasingly being stretched to the limit.
"Staffing shortages are all too apparent on units and the care of our most vulnerable babies is being compromised.
"No other critical care service would permit the capacity and staffing levels seen on special care baby units.
"While some extremely welcome progress has been made in the past year, there is still much more to do.
"Action is urgently needed to invest in our special care baby services, both now and for the future."
A spokesman for the Department of Health said: "We welcome the publication of the Bliss Baby Report 2008.
"The Government is committed to provision of safe, high quality neonatal services.
"There is no evidence that neonatal services are unsafe.
"The introduction of neonatal networks in 2003 has led to a number of improvements, including a reduction in long distance transfers of mothers and babies, and an increase in intensive care capacity.
"However, we recognise there is still more to do and that is why we have established the Neonatal Taskforce to support the NHS to identify and deliver further improvements to neonatal services."