Babies born or admitted at times when units were becoming busier were at higher risk of mortality than infants admitted at less busy times

Dr Janet Tucker, University of Aberdeen

The study, published in The Lancet, looked at whether a range of factors including patient volume, staffing levels, and workload were linked to death and brain damage rates and the incidence of hospital-acquired bacterial infection.

It looked at 13,500 infants admitted to 54 randomly selected units across the UK.

There were just under 400 deaths in hospital, 65 of which were attributable to conditions present at birth or complex heart surgery.

All units were categorised based on numbers of infants treated and numbers of nurses and doctors as high, medium and low volume units.

Size 'unimportant'

Although high-volume units treated the sickest infants and had highest crude death rates, when the statistics were adjusted for factors such as the severity of the illness, patient volume and staffing provision, unit size did not influence death or brain damage rates.

If a smaller unit was looking after a very sick baby, it was transferred to one which could provide a higher level of care through the network of units, the researchers found.

But infants were at greater risk when units were busier, whatever their size.

Dr Janet Tucker, a senior research fellow in the department of obstetrics and gynaecology at the University of Aberdeen told BBC News Online: "Babies born or admitted at times when units were becoming busier were at higher risk of mortality than infants admitted at less busy times."

She added that nurse staffing levels across units were consistently about 10% below national recommended standards.

"Further improvement of outcomes for infants may be brought about by improving nurse staffing levels; especially avoiding occasions when units become very busy and the availability of skilled nurses to care for infants falls," she said.

'Unrepresentative'

Professor Murray Pollack, and colleagues from the George Washington University School of Medicine, USA, also writing in The Lancet, welcomed the UK research, but said "things had moved on" since it started.

"Factors such as volume of patients and total staff numbers no longer adequately represent what is really happening at the bedside."

Dr Harvey Marcovitch, spokesman for the Royal College of Paediatrics and Child Health, said the sickest babies needed almost constant observation.

"You almost can't leave them for a moment."

He said sometimes even looking after two babies was too high a workload for one nurse because problems could occur extremely suddenly.