Staff and bed shortages force maternity closures
Many NHS trusts in England had to shut their maternity units in the past year, with the most common reason being a lack of staff or beds.
Data obtained by the BBC under the Freedom of Information Act showed 62 trusts out of 121 respondents - or 51% - temporarily closed units in 2013.
In 2008, Conservative Party research found 42% of trusts shut their maternity units at least once.
Health minister Dr Dan Poulter said units closed on "limited occasions".
He said the government had "increased choice in maternity care", saying the number of midwifery-led units had almost doubled since 2010.
"There will always be very limited occasions when a maternity unit cannot safely accept more women into their care and may need to close temporarily.
"Any decisions to redirect women are made by clinicians as part of a carefully managed process," he said.
Dr Poulter said the NHS, which has 162 trusts in England, remains "one of the safest places in the world to give birth".
The latest figures come after the Conservative research in 2008 found that one in 10 trusts had been forced to close their unit 10 times or more.
The 62 trusts identified this time represented 51% of those that responded to the BBC Freedom of Information request. Some 12% had closed their units 10 times or more.
Many were for just for a few hours, but there were examples of wards closing their doors to new patients for more than 48 hours until pressures had eased.
Nottingham University Hospitals NHS Trust closed the most times, with 97 closures across two hospitals - the Queen's Medical Centre 48 times and Nottingham City Hospital on 49 occasions.
|Highest number of closures|
|Trust||Number of closures|
|Nottingham University Hospitals NHS Trust||97|
|Leeds Teaching Hospitals NHS Trust||89|
|University Hospitals of Leicester NHS Trust||86|
|Heart of England NHS Foundation Trust||50|
|Queen Elizabeth Hospital King's Lynn NHS Trust||24|
This was followed by Leeds Teaching Hospitals NHS Trust, with 89 closures across its two hospitals - Leeds General Infirmary, 60 times, and St James's University Hospital, 29 times.
In Wales, six out of seven health boards responded. Four had experienced closures.
Scotland and Northern Ireland did not report any closures.
The findings come after a poll last year by the Care Quality Commission showed the maternity system in England was under strain.
A quarter of women reported being left alone during labour and birth at a time that worried them.
There are currently nearly 22,000 midwives in the NHS in England - a rise of more than 1,700 in four years.
But the Royal College of Midwives (RCM) believes there is a shortage of 4,500 because the birth rate is at its highest since the early 1970s.
However, the demands being placed on the service are also related to the larger number of complex births being seen because of factors such as obesity and multiple births linked to fertility treatment.
RCM chief executive Cathy Warwick said: "Birth is unpredictable and sometimes units get a rush of births that is unavoidable and cannot be planned for.
"However, if units are regularly and persistently having to close their doors to women it suggests there is a serious underlying problem."
Elizabeth Duff, of the National Childbirth Trust, said: "This failure of maternity services can mean women get passed from pillar to post when having a baby. This is hugely disruptive to labour."