Maternity services are under threat because too few women are using the facilities at Grantham Hospital, hospital bosses have said.
In 2007, 84 babies were born at the midwife-led unit and despite this number rising to 121 in 2008, bosses said the target of 300 needs to be met.
Only women who have no complications in their pregnancies and have a straightforward birth can use the unit.
Emergency surgery services at Grantham were closed in 2007.
When the United Lincolnshire Hospitals NHS Trust announced the changes in 2007, it said midwifery services would be reviewed in 18 months' time. The review has begun and a report is expected in October.
Grantham Hospital midwife Marie Robinson said the unit was very important to women in the area.
"This is an essential service for these pregnant women here," she said.
"They've been devastated by the loss of the full maternity services and we want to try to keep this little unit open if we can, to offer as much choice as we possibly can.
"We provide an excellent service here. Women value it tremendously but we can only up the numbers if women are low-risk and deliver safely here."
Women who cannot use Grantham's services currently have to travel to Lincoln, Boston, Nottingham, Leicester or Melton.
If more babies are not born at the maternity unit, it may be forced to close
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