Is preconception planning common sense, or just another pressure on future mums? Celia Dodd finds out
Six months before she started trying to conceive each of her three children, Elizabeth Fairley went on a rigorous detoxification programme. She exercised regularly, gave up alcohol and white sugar, filtered all drinking water and ate a wholefood diet plus a combination of more than 30 vitamin and mineral supplements. "I hadn't had any problems with infertility or miscarriage myself," she says, "but it seemed to me to make total sense to follow a prevention programme as a routine. As a result I never worried at all about the health of any of the babies. I was 39 when my third baby was born, 18 months ago, but I felt totally confident that she would be all right."

Increasingly, women who are considering pregnancy are exhorted to follow the example of women like Elizabeth. It is no longer considered good enough to give up alcohol, cigarettes and soft cheese as soon as the pregnancy test is positive. Now, the pressure is on women to get into top physical and emotional shape long before they even start trying to conceive. Self- help books and videos, magazine articles and adverts for pre-pregnancy multivitamin supplements now tell women to radically change their lifestyle at least six months before conception. Private clinics offer a range of services, from checks for infection to hair analysis to detect toxic metals in the body.

It is not simply a question of creating a superbaby; the new fundamentalist reasoning insists that if women don't follow the rules, they risk damaging not only their children's health but that of future generations. The list of possible consequences - from congenital deformity and cot death to delinquent children and mental problems - is dire.

Women could be forgiven for taking a sceptical view of yet another set of rules - after all, the goalposts are constantly shifting when it comes to guidelines on pregnancy. Many doctors are also cautious. Peter Saunders, consultant in obstetrics and gynaecology at University College Hospital, says, "I'm not in favour of hard and fast rules. Certainly women should think about their lifestyle before they get pregnant but not go over the top, and not get obsessive. To say you can't have a cup of coffee or glass of wine is absolute madness."

Even so, pre-conception advice, however extreme, is hard to ignore; the stakes are too high. But one fact cannot be ignored: there will always be a risk of imperfection, no matter how hard we try to control a pregnancy. Elaine Bridges, whose son was born a year ago, when she was 39, was given one of these books, Planning A Baby? by Dr Sarah Brewer. She remembers, "I'm sure a lot of what it said was absolutely true, but it was terribly finger-wagging and censorious of women who want to have a bit of fun." Elaine's personal targets included taking folic acid supplements three months before she tried to conceive, recommended by the Department of Health to prevent neural tube defects such as spina bifida. Other precautions, such as checking your immunity to rubella, are also worth taking.

But the gulf between such obvious good sense and the extreme advice offered by fundamentalists in the field, such as Foresight, the Association for the Promotion for Preconceptual Care, is huge. Nim Barnes, who founded the association nearly 20 years ago, is unrepentant: "I'm a complete perfectionist with babies. I am always amazed how gung-ho people are. So much of child illness comes from what happens before conception."

But pregnancy doesn't always happen when you want it to. So women who decide to go for the six-month limber up may well find that it stretches to a year or even longer, their changed lifestyle a constant reminder of the state they haven't managed to achieve. By the same token, some 40 per cent of pregnancies are accidents. So how does pre-conception advice affect women who haven't planned to get pregnant? Hedda Archbold had always intended that she and her partner would prepare for conception for about a year: "I felt it wasn't just my body that had to be in good shape but his sperm, too. But in the end my first pregnancy was a total accident. At first, I thought I can't have this baby, partly because I was in really bad shape the month I actually conceived. I'd been very stressed and was drinking and smoking heavily. I worried about the baby's health throughout the pregnancy, although I gave up everything as soon as I knew I was pregnant. But he was fine, so the second time round I was more blase."

As Director of the Birth Control Trust Ann Furedi fields large numbers of calls from women like Hedda. Some even consider an abortion solely on those grounds. She says, "The overwhelming majority of babies are born healthy, pretty much no matter what the woman was doing at the time she conceived. The thing about health promotion in pregnancy is that it focuses people's minds on what are, in fact, quite small risks." Charlotte Evans, one of the dietitian who run the Sainsbury's/Wellbeing Eating for Pregnancy Helpline, also regularly reassures women who feel anxious either because they haven't taken folic acid or, more often, because they have got drunk in the period around conception. She says, "Even if you've been rushing about, drinking, smoking and living on TV dinners, the chances are you're still going to have a healthy baby."

Although an upsurge of academic interest in pre-conception must be good news for couples who find it hard to conceive, it is a notoriously difficult area to research. A great many factors come into play - the most significant of which appears to be social class - and it is often impossible to draw clear-cut conclusions. David Paintin, former consultant in Obstetrics and Gynaecology at St Mary's Hospital in West London, says, "The causes of foetal abnormality are still not thoroughly understood. I think it will be at least 10 years before we have practical policies."

Meanwhile, most women prefer to trust their own instincts. Zoe Coleman gave birth to a healthy, 7lb daughter, Natascha, last month: "I reckoned I was reasonably healthy anyway, so I thought I wouldn't be fanatical about it. Is it better to be stressed out and stop everything or to be more relaxed and do a little of whatever makes you feel good?"