Mismanagement of NHS finances has led to 43 maternity units being closed or facing the threat of downgrading or closure, according to the Conservatives.
Twenty-one midwife-led units and 22 consultant-led units are under threat, the majority of which are located in opposition MPs' constituencies.
Six out of ten of the threatened maternity units are operated by providers which finished the 2005-06 financial year in deficit, the Conservatives revealed.
Shadow health secretary Andrew Lansley said that maternity units were "the latest frontline service to bear the brunt of Labour's financial mismanagement of the NHS".
"The government talk about delivering choice to mothers, but cutbacks are taking that choice away," he insisted.
"There is little logic behind these reconfigurations - the only pattern appears to be that units with fewer than 3,000 births a year are being targeted for closure."
Mr Lansley said that deficits were leading to patients being denied accessible local services, although a Department of Health spokesperson insisted that it was "the quality of service, locality by locality that matters, not the number of units".
However, many parents-to-be are abandoning the NHS, preferring to attend private maternity hospitals rather than visit clinics that are a long way from home.