Maternity units are more likely to close their doors to women in labour at the weekend when there are fewer staff.
An investigation has found that the chances of a department shutting on a Saturday are 59 per cent higher than on a Wednesday.
It also showed that at least 30 per cent of closures were due to staffing problems, rather than the unit being very busy.
Maternity units are increasingly closing their doors, temporarily, when they are either very busy or understaffed.
Maternity units are more likely to close their doors to women in labour at the weekend when there are fewer staff (stock image)
Women who had planned to give birth are diverted to other hospitals nearby, which can be a distressing experience during labour.
But an analysis by the Institute for Fiscal Studies think-tank has found there are typically more closures on Fridays, Saturdays and Sundays, when fewer staff are on duty.
Figures obtained from Freedom of Information requests show there were an average of 65 closures per 100,000 admissions on a Saturday between 2011 and 2015.
This compares with 41 per 100,000 on Wednesdays over the same period. Units were more likely to close in December – when staff were off for Christmas – compared to other months of the year.
But the worst month for closures was September when more babies are born, having been conceived during December and January.
Elaine Kelly, a senior research economist at the Institute for Fiscal Studies and an author of the study said: ‘NHS maternity units are more likely to close towards the end of the week and during holiday periods, pointing to staff availability as a key problem.
‘Such closures may be the most cost-efficient way of dealing with pressures but NHS hospital trusts should certainly ensure that such day-of-the-week or seasonal effects are an understood and tolerable consequence of financial restraint, rather than the result of poor workforce management.’
A separate investigation by Labour last month found that half of maternity units had closed their doors at least once in the past year. There were 382 temporary diversions, a rise of 70 per cent compared to the previous year.
NHS maternity units are more likely to close towards the end of the week and during holiday periods
When a maternity unit imposes a diversion, staff contact women in labour and tell them to go to another hospital.
In some cases this can be 50 miles away – an hour’s drive – if the nearest maternity units are also very busy.
Maternity units are under pressure due to the higher number of complex labours among women who are older or obese.
The birth rate has stabilised in recent years but it is still considerably higher than a decade ago.
Unions say the number of midwives and specialist doctors have not kept pace with demand and claim staffing levels are sometimes dangerously low.
Jon Skewes, director for policy, employment relations and communications at the Royal College of Midwives, said: ‘There is a cocktail of a historically-high birthrate, increasingly complex births and staff shortages that lead to units closing temporarily.
‘Heads of midwifery tell us that pressures on services are leading to closures and also to the temporary removal of services such as home births.
‘The solution in essence, is fundamentally simple, and that is to fund and staff our maternity services so that they have the resources to meet the demands being placed on them.’