More expectant parents are being denied a choice of where they can have their baby, campaigners have warned.
Campaigners are calling for parents to have more choice
The National Childbirth Trust says at least 10 birth centres across the UK are now considering closing, or are definitely set to do so.
Some "temporary" closures over Christmas may become permanent due to a lack of funds, the NCT says.
But the Department of Health said local health services had the funds to provide adequate maternity services.
Birth centres are smaller than hospital units, and are not run by consultants.
They focus on ensuring births are as natural as possible.
They account for about two per cent of births in the UK. But they are sometimes under-used. The NCT says GPs often do not give women the confidence to try them.
There are around 100 such centres across the UK.
The NCT said in November that six units were under threat.
But it now says centres in Dover, Petersfield, Fareham, Southport, Devizes, Malmesbury, Wakefield, Guisborough and Romsey are under threat, or had recently been closed.
Birth centres in Grampian are also threatened with closure, they suggest.
Some centres have been closed temporarily, but the NCT says there are fears they will not re-open.
Belinda Phipps, chief executive of the NCT, said: "With Christmas coming up we've seen a sudden increase in the numbers that are closing - theoretically temporarily, but it's quite astonishing how often that temporary closure turns into a long term closure and once they're gone they're gone, and it's very difficult to get that sort of service back.
"The NHS requires them to be in place, but if they're not we really worry that they won't ever come back."
The NCT warns the government's plans to improve maternity services - as set out in the National Service Framework for Children, Young People and Maternity Services - will be jeopardised unless the government backs community-based birth centres.
Ms Phipps added: "We know that access to birth centres helps to increase normal birth rates, giving women with a straightforward pregnancy a better chance of giving birth without drugs, forceps or emergency surgery."
But she added: "Many women are not being encouraged to consider the full range of choices for birth. As a result, birth centres in some areas appear unpopular, underused by women and unsupported by the local community.
"We fully support government pledges to increase choices for women over where and how they have their baby. Yet their worthy aims are being undermined by the short-term financial difficulties of NHS trusts.
"We are urging the government to consider the needs of the modern day "Mary and Josephs" and support community birth centres."
But a Department of Health spokeswoman said: "Of course, expectant parents will be able to access maternity services over the festive period."
She added: "Record investment in the NHS means that local primary care organisations and hospitals have the resources to deliver high quality maternity services.
"It is up to local service providers to decide how best that extra investment can be spent to meet the needs of their local communities."
And a Scottish Executive spokeswoman said: "We do not recognise these claims at all.
"Our commitment to community midwife units is well documented and this is set to continue."