"I trusted her so much," says Michelle Fleming. "The pain was outrageous. I was going crazy, gyrating - almost dancing - but I knew I was safe because she was there, in the next room." Michelle, alone in her darkened bedroom, was minutes away from giving birth to her first child. "I reached a crescendo and screamed, 'It's coming,' and they rushed in - she grabbed me and lifted me up and Ruby just popped out, still in her waters."

If, like me, you gave birth strapped to various machines in a bright room surrounded by medical professionals wearing masks and injecting you, then you'll no doubt be tempted to put this newspaper straight in the bin. This is, indeed, the kind of birth story designed to persecute us.

It took only five hours from Michelle's first twinge to her moment of glory and she describes the whole experience as "amazing" and "fantastic". Lucky her then? Well, there may have been more to it than luck.

The woman Michelle trusted so much is Lilliana Lammers, her "doula". A doula (the word comes from the ancient Greek, meaning, roughly, "handmaiden" or "servant") does not deliver babies. She is a "mother figure", there to give continuous physical and emotional support to a woman before, during, and immediately after childbirth. A doula must have given birth herself and may have been trained in the physiology and psychology of birth. But, unlike your real mother, she won't criticise and she won't tell you what to do.

Doulas have for several years now been a familiar presence in labour wards across the US, where most babies are delivered by an obstetrician and levels of intervention are high. Thanks to celebrity mothers like Elle Macpherson and Rikki Lake, who both hired doulas, the popularity of this hired mother figure is greater than ever.

But it's not just American celebs being trendy. Doulas, numerous studies show, do make a difference. One recent report found that with a doula present, labour is 25% shorter, the need for epidural pain relief is 60% less and the caesarean section rate is reduced by half. And the benefits of doulas have even been recognised by the World Health Organisation, among others.

They can help postpartum, too: a 1998 US study found that women who had doulas during labour were more sensitive, loving and responsive to their infants two months later than those who'd gone it alone (since the doulas were assigned at random in the study, it wasn't simply a case of those who chose to have one being innately more nurturing than the others).

As the root of the name suggests, the doula role is not new: in many cultures a mother or a sister habitually does the job. But if the thought of your mother barking instructions at you between contractions is not a comforting one, don't worry: more and more women in Britain are turning to doulas.

Midwives have traditionally been women's greatest support during labour, but nowadays staff shortages mean that continuous care isn't always possible when you're giving birth. When I was in labour, a year-and-a-half ago, I saw seven midwives, one after another - I barely had time to learn their names, let alone build a trusting, reassuring relationship with any of them.

Dr Michel Odent, the obstetrician best known for "inventing" the water birth, thinks this is the nub of the problem: "Many women giving birth today will see several midwives during labour, but what a woman really needs is one mother figure with her throughout the birth."

But couldn't the presence of a doula lead to confusion in the labour room? In the US, where the role has been clearly defined (Doulas of North America is the main coordinating body - it has 2,800 members and offers training and certification), doulas are seen as a complement to midwifery services. As Debra Pascali-Bonaro, an American doula, explains: "At moments when a woman in labour needs medical care, a doctor or midwife is busy providing medical support but a doula can offer emotional support to the woman."

So, too, can your husband or partner, of course, but the idea is that your doula will be less emotionally involved, and her experience of childbirth will give added reassurance when you need it most. If you want a doula in Britain, you might try Top Notch Doulas, who select and train their women themselves. But agency prices will put them out of the range of most budgets (a Top Notch doula will cost you a £125 agency fee, £150 for the birth itself and £10 per hour thereafter). But their approach is professional: Top Notch's director, Jean Birtles, recently established a coordinating body - the British Doula Association - and hopes to gain formal recognition from organisations such as the Royal College of Midwives.

But most people in Britain still find their doulas by word of mouth. Odent believes this diversity is valuable. He thinks a doula can't be "trained", only "informed": her role is more about who she is than what she does. "The key to success," he says, "is finding someone you can relate to."

Michelle certainly believed in her doula, Lilliana. With four children of her own, Lilliana has firm opinions about childbirth: "Women don't need help to give birth," she says. "We just need peace and quiet and safety." She likens giving birth to making love. "If you're cold, it doesn't work; if someone interrupts you, it doesn't work. You need to be somewhere that you feel safe, where no one is going to disturb you, where you have privacy, warmth, no bright lights."

This sounds perfect if, like Michelle, your labour is straightforward, but what about foetal distress? Breech births? Complications? "I don't mean the midwife shouldn't be there," Lilliana explains, "or that you have to be at home." But even at hospital births she considers her role to be "keeping everyone from disturbing the woman". For safety's sake, she says, the midwife must be allowed in to monitor the baby - but she should not speak to the woman, or move her or disturb her unless she has to. Meanwhile, the husband or partner should sit silently in the room, or supportively outside it, depending on the woman's wishes.

There are, of course, obvious dangers in placing so much trust in one individual. While Lilliana is clearly a sensible, well-informed woman there's always the possibility that you'll get a rogue doula - one, say, who advises you not to listen to your obstetrician, or who tells you your newborn's 39C (103F) fever is normal.

"This is why we want to get our doula training to a standard that the Royal College of Midwives supports," says Birtles. Top Notch Doulas turn trainees away if they are "too bossy, or likely to impose their views, for instance on drugs, during labour, or infant vaccinations". And they believe it is crucial that the doula herself has had a positive experience of giving birth. "The last thing you need in a birthing room," says Birtles, "is fear."

Birth can be scary enough: pain, blood, hospitals, strangers. I'm certainly considering having a doula with me for the birth of my next baby. My husband was a huge support last time, but, like me, he was a novice and at times (like me) was alarmed and uncertain. So when the contractions kick in next time, I can't help thinking a bit of motherly reassurance would do us both good.