Maternity units at a hospital trust in England had to close 97 times in the past year, figures show.
The closures across Nottingham University Hospitals NHS Trust, which covers Nottingham City Hospital and the Queen's Medical Centre, were revealed after a Freedom of Information request by the BBC.
Just over half of the trusts who responded to the request for information had to close for a time in 2013.
The main reasons for temporary closures were lack of staff and beds, the BBC said, adding that many of the closures lasted a few hours but some were closed for more than 48 hours.
Of the Trusts in Wales who responded four had closed for times ranging from short periods to over 24 hours.
Trusts in Scotland and Northern Ireland did not report any closures, the BBC said.
Chief executive of the Royal College of Midwives Cathy Warwick said regular or persistent closures suggest "a serious underlying problem".
"Birth is unpredictable and sometimes units get a rush of births that is unavoidable and cannot be planned for," she told the BBC.
"However, if units are regularly and persistently having to close their doors to women it suggests there is a serious underlying problem."
Commenting on the figures health minister Dr Dan Poulter said mothers-to-be were being offered more choice.
He said: "We have increased choice in maternity care. The number of midwifery-led units has almost doubled since 2010 and more women live near a range of services to choose from.
"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.
"Our NHS remains one of the safest places in the world to give birth and the latest independent CQC (Care Quality Commission) survey found that maternity care in England has improved, with women reporting high levels of trust and confidence in staff caring for them.
"We have invested £35 million to improve maternity units across the country and now have over 1,700 more midwives - with 6,000 more in training since 2010."