The NHS has admitted it does not know why Birmingham has the worst infant mortality figures in the country.
A House of Commons inquiry warned that “unexplained variations” between the death rate in different parts of Britain may be due to poverty and other social factors - or to poor medical care.
But senior health managers did not know the answer, because of “limited data” about patients, the inquiry warned.
The Midlands South neonatal network, which includes hospitals in Birmingham, Solihull, Herefordshire and Worcestershire, has the highest rate of infant mortality in the country - with 4.8 deaths per 1,000 live births in 2005. Many of the children affected were born prematurely or suffered from an illness or defect which meant they required neonatal care.
The Midlands North neonatal network, which covers Shropshire, Staffordshire, Wolverhampton and the Black Country, had the second worst record in the country, with 4.3 deaths per 1,000 live births.
By contrast, The Surrey and Sussex neonatal network has a death rate of 1.8 per 1,000 live births, the lowest in the country.
During the inquiry, it emerged that the NHS did not know whether this variation reflected the quality of medical care or other factors.
Sir Bruce Keogh, Medical Director of the NHS, told MPs that the data “takes no account of the nature of the babies that appear at the front door of the neonatal intensive care unit.”
He added: “There is a variety of factors that influence how those babies are likely to do. One would be the socio-economic group . . . others would be things like the size, eight and gestation period of the baby and so on.”
He admitted that the NHS did not know if any of the neonatal networks were offering poor medical care.
David Nicholson, the NHS chief executive, told the inquiry: “Progress here has been fraught by a lack of national data with which we can work.”
They were giving evidence to an investigation by the House of Commons Committee of Public Accounts, which includes Shropshire MP Philip Dunne (Con Ludlow).
Publishing its findings yesterday, the committee warned: “The NHS still has limited data on patient outcomes, other than mortality rates which show unexplained variations between networks.
“While these variations may be due to the demographics of the population covered by the network, such as high and low maternal age, obesity and smoking, other factors, such as access to care during pregnancy and speed of access to the right level of neonatal care, may also have an influence.”
The Healthcare Commission, the official NHS watchdog, has launched a review to try to determine why death rates are higher in some regions than others.
The committee also warned that there was a “serious” shortage of nurses providing neonatal care, and hospitals were struggling to meet demand.
Each of England’s 178 neonatal units had to close its doors once a week on average during 2006-07.
The cross-party group of MPs also found that a third of neonatal units operated above the recommended occupancy rate of 70 per cent.
They said: “High occupancy rates could have major implications for patient safety due to increased risk of infection or inadequate staffing levels”.
Only half of networks provide specialist neonatal transport services at all times, and the committee found that almost three quarters of units had experienced delays in transporting babies as a result.
Dr Sheila Shribman, the Government’s national clinical director for children, young people and maternity services, welcomed the report.
She said: “We are committed to delivering real improvements for mothers and babies and have made neonatal services a top priority for the NHS.
“Spending on neonatal services increased from £655 million in 2003-04 to £802 million in 2006-07 - an increase of 22 per cent.”
She added: “We have established a Neonatal Taskforce to support the NHS to identify and deliver real improvements to services.”