Of the 70% of hospital trusts that provided data, more than 40% said they had been forced to shut their doors or divert women to other sites at least once. One in 10 said it happened more than 10 times, according to reports.
The figures were obtained in a freedom of information request made by the Conservatives.
The Government said maternity units sometimes were forced to take action because it was hard to predict demand.
Of 103 trusts providing maternity services that responded, 42% had to close their units or divert women to another site at least once in 2007 because of capacity problems.
The Tories said that of those trusts that had to turn women away, 74% had more than 3,000 births last year, suggesting large maternity units seemed to be more at risk of having to close.
A Department of Health spokesman told the BBC diverting women to other hospitals should be the exception rather than the rule.
“It is difficult to precisely predict when a mother will go into labour and sometimes, at times of peak demand, maternity units do temporarily divert women to nearby facilities,” he said.
“When this does happen it is often only for a few hours and to ensure mother and baby can receive the best care possible.”