Services for critically-ill newborn babies are severely understaffed and could soon be stretched even further by restrictions on doctors' working hours, it was claimed today.

Researchers in Yorkshire based their findings on the number of transfers of newborns and pregnant mothers about to give birth from local maternity units to specialist units.

Transfers are necessary when local specialist expertise is not available, or when demand exceeds capacity.

Between May and November 2000, 800 transfers were made to specialist centres across Yorkshire. Almost half were women about to give birth, and the majority of these were "acute" cases requiring urgent action.

Of the total number of transfers, 152 came from level-two or three units, which offer advanced services for "at risk" cases. In theory, they should have been able to provide services on site, said the authors, led by Dr AB Gill, at Leeds General Infirmary.

The transfers occurred because the units were already at the limit of their capacity in terms of cot availability and staff numbers.

Almost four out of ten transfers were from two level-three units.

One in six of the 254 newborns transferred out of an intensive care unit were sent to hospitals some distance away, suggesting a lack of available capacity.

The researchers pointed out that the problem was unlikely to be confined to Yorkshire.