Over the next few weeks, hundreds of people will crowd into halls across Britain to see a film that has been grabbing the headlines in the US. Called The Business of Being Born, it's a documentary by chatshow host Ricki Lake, about birth and specifically why pregnant women need to reclaim the right to give birth without unnecessary intervention. In the US, birth rights are pitiful, with home birth banned in 10 states and the caesarean section rate standing at one in three. Only 8% of women are able to use midwives, who specialise in natural birth, and instead have to see obstetricians, whose metier is highly interventionist hospital delivery.

The Lake film has led to a campaign in America called The Big Push for Midwives, and the ambition is to enable more women to use the services of a midwife and to overturn a culture in which intervention is overwhelmingly the norm.

Over here, the film's effect could be equally significant. It is being screened at venues across the country by the Independent Midwives Association (IMA), and when the lights go up the audience will be urged to bombard the chief executives of their primary care trusts with letters and emails asking for better facilities for home birth.

"We're at the tipping point," says midwife Annie Francis of the IMA. "We've been fighting for decades for home birth to be available in Britain again and now our moment has come. Home birth is already on the increase - up from around 1% 15 years ago to around 3% today. And last year a government report, Maternity Matters, said women who want a home birth should be able to get one. The tide really is turning." The campaigners' main aim is to ensure that the government sticks to its promises.

It is a big turnaround when you consider that for many years it was government policy that all births should happen in hospital. The Peel Report of 1970 made that its central ambition. Maternity Matters, in contrast, promises mothers-to-be a "full range of birthing choices": a home birth, birth with midwife care or birth in the care of a consultant. And there's plenty of evidence that where home birth is well supported, it's popular: areas such as West Somerset and Mid Suffolk, for instance, boast well above average rates (14.2% and 11.6% respectively).

All of which is great news for the grassroots activists who have been fighting for years for a woman's right to labour upright, without unnecessary machines, in her own home. Ricki Lake exemplifies such women, having been inspired to speak out by her own experiences. In her film, she describes how disempowered she felt as a result of the hi-tech arrival of her first child, and how fired up she was after the birth of her second child at home. Spreading the gospel that birth could be low-tech and without drugs or machines became what she calls her "passion project".

Other campaigners have been more modest but equally effective. Civil servant Michelle Barnes, who organised a conference on this subject last month in her home town of Sheffield, says: "Things changed for me after I had a home birth two years ago. My first child had been born in hospital after a heavily medicalised labour that led to a caesarean. I might have had a home birth the first time round if I'd known anything about it, but I didn't. After I had a home birth, I wanted to inspire and encourage others who might be interested." Her conference brought together 170 people. "Home birth is already above average here in Sheffield, at around 4%, and now we've got a head of steam it's going to go up and up," she says.

After her first experience of home birth 10 years ago, Angela Horn set up homebirth.org.uk to debunk the myths about how unsafe home birth was. The research she summarises on her website includes the 1997 National Birthday Trust report, probably the most comprehensive study of UK home birth to date, which found that it halves the chance of needing an assisted or caesarean delivery and that babies born at home are less likely to need resuscitation. Another British report found that the perinatal mortality rate in planned home birth was less than half the average for all births.

"In my first pregnancy I started reading the medical research," says Horn, "expecting to find that home birth provided a more pleasant experience but had a pay-off in terms of higher mortality rates - only to find that there was a growing body of evidence showing that home birth for healthy women was remarkably safe. After I had my first baby, I felt 10ft high. It's incredible how a good birth can change a woman. You've brought new life into the world, and you've done it yourself rather than, as happens to so many women, finding yourself at the heart of a crisis that you need to be rescued from."

Horn realised that women who might be interested in a home delivery were often put off by the lack of unbiased research that challenged the status quo - in other words, no one was publicising the studies that challenged the assumption that hospital birth was safest. "Sure, there will be babies who die at home who wouldn't have died in hospital," says Horn, "but the other side of that is there are babies who die in hospital who wouldn't have died at home - the ones who get MRSA among them. It's very difficult to say in absolute terms whether home or hospital is less likely to end with a death, because, thankfully, birth is in general very, very safe in the UK. But what's clear is that there's no big difference between the two."

Some women have gone into midwifery after becoming passionate about home birth as a result of their own experience. Annie Francis says her life was changed when she had a hands-off delivery with a breech baby - her first - after being told a caesarean section or assisted delivery were her only options. "Three babies on, aged 40, I retrained as a midwife," she says. "I thought I could provide one-to-one care through a career with the NHS - but I found that wasn't possible because of the way the maternity services are organised, so I became an independent midwife working outside the health service.

"I feel I've been able to pioneer a model of care that's truly women-centred, and the exciting thing is that the government is now beginning to recognise that. The new health and social care bill contains a clause to allow primary care trusts to contract independent midwifery services in, which means that instead of paying £2,000 or so for the sort of individual, tailored service I provide, in the future women will be able to get my services on the NHS."

Other campaigners have been fired into action not by a happy childbirth experience, but by a terrible one. Mary Newburn, head of policy research at the National Childbirth Trust, decided that conditions for women had to be improved after the hospital delivery of her first baby when she was 18, three decades ago. "What happened to me was brutal," she says. "I was left all alone, lying on a bed with an oxytocin drip in my arm, which made an already painful labour sheer agony. I thought I was going to die there; the horror of it, and the horror that any woman in labour could ever be treated that way, has never left me." Afterwards, Newburn dedicated herself to researching childbirth. She went on to have three happier births, two at home, but it is the fear and isolation she felt during her first delivery that has spurred her on.

For many women who are interested in home birth, the biggest stumbling block up until now has been the absence of someone to talk to who has experienced it. As the culture shifts hopefully all that will change.