It is the miracle that can become a nightmare. A slip-up with the sperm - or an accident with the eggs - and a white woman gives birth to black twins. A black couple wishes to claim the twins; the woman who gave birth to them wants to keep them. The story is terrifying, its ethical and legal implications hard to disentangle.

Only a few days earlier, there was another warning on IVF - about undergoing treatment too soon. Scientists at the European Society of Human Reproduction and Embryology conference in Vienna questioned the wisdom of pronouncing a woman infertile after only one year, believing she should wait at least two before seeking treatment.

These stories, although unrelated, concentrate the mind on what is involved for every woman who puts her fertility into the hands of doctors but neither addresses the greatest - and most common - gamble of IVF.

A couple with triplets walk into a room. Not a word is spoken. They manhandle a double buggy, unravel a third baby from its sling. For 10 years, they have been longing for a baby. Now, they have three - alive and crying. The parents look extinguished.

A scanner tells a woman she is expecting triplets. The woman is so shocked and distressed that she has to be sedated before leaving the hospital.

The father of new-born triplets cracks this serious joke: 'My wife used to cry because she didn't have any children. Now she cries because she has too many.'

Everyone is warned that IVF treatment may fail. But not enough women (30,000 seek treatment in this country every year) seem fully aware of the multiple ways in which it can succeed. Once 'higher order multiples' - triplets and quads (more catchily known as super-twins) - were a rarity. In 1839, Queen Victoria decided to reward families of triplets, giving a guinea to each child as a mark of her respect. Nowadays, she would have to part with her bounty far more often.

Twins are commonplace (about 8,500 sets are born in Britain each year, compared to 6,400 in 1980) and the number of triplet births since 1980 has risen from 91 to 262. Of these, about 15 per cent are conceived spontaneously, 50 per cent through IVF, and the rest through other fertility treatments.

What is the effect of these super-twins on families? Mothers have only two hands, two breasts. Children have only two parents. At present, it seems that neither families, social services, nor schools are adequately prepared for multiples. Last week, Tamba, the Twins and Multiple Births Association, drew attention to primary schools that fail to offer places to sets of twins and triplets, unaccountably unwilling to see them as siblings.

Insufficient information is a problem even before conception. Jane Denton is director of the Multiple Births Foundation, a charity that supports families of multiples through educating and training professionals. IVF clinics licensed by HFEA (the Human Fertilisation and Embryology Authority) are required by code of practice to give counselling about the risk of multiple pregnancy. But, she says, it is hard for couples to consider what it might mean for their treatment to fail and, at the same time, to imagine the opposite outcome, a family of multiples. 'The enormous question is to what degree people really understand the information. I don't know if you can prepare people.'

In Sweden, it is illegal to put back into a woman more than one fertilised embryo at a time. It is recognised that multiple births are not a desirable outcome of IVF. In this country, the British Fertility Society and the Royal College of Obstetricians and Gynaecologists (RCOG) give guidelines that IVF doctors should not transfer more than two embryos at any one time. And a further HFEA ruling will make it harder for clinics to be cavalier about the number of embryos they replace. However, there is still no law against transferring three embryos and private fertility clinics can - and do - ignore these guidelines if they choose.

Fertility clinics are a multi-million pound industry. Like private schools, they have their league tables. An alarming report in New Scientist suggests that private clinics are self-servingly focused on these tables. To secure the best results, they tend to be highly selective about the cases they will take on (only younger women need apply). There is also a strong temptation (and one that parents may share) to up the chances by implanting several embryos with each treatment. It could be seen as better value; a single cycle costs about £2,000, but there is no additional charge for extra embryos.

Hossam Abdalla, director of the Lister Fertility Clinic in London, told a conference in Montreal: 'We have moved from the age of the multiple baby to the age of the litter' and added frankly: 'If you want to do well in the tables, you put in more embryos.

'In women above the age of 40, when the chances are pretty slim, transplanting three or even four embryos is not wrong. A blanket policy against this would be inappropriate.'

Dr Brian Lieberman, at St Mary's Hospital, Manchester, is a pioneer in reproductive technology and a passionate advocate for limiting the number of replaced embryos to two. 'There is no justification, under any circumstances, in putting back three embryos,' he says. 'Let us take as a starting point the welfare of the children. Most triplets are born prematurely at 32 weeks or earlier. Some are born at 26 or 27 weeks. There is a much higher risk of them dying, or of having cerebral palsy, blindness, deafness, developmental disorders.'

It is not the would-be parents, he says, but the medical profession that needs to be educated. 'I understand it from the couple's point of view. When I talk to an infertile couple and I warn them that they may have twins their eyes light up ... but four per cent of twins die in the first week of life, and nine per cent of triplets.'

Sometimes parents are thrilled to be told the mother is pregnant with three, feeling that it must be three times as good as one. But when, as sometimes happens, some or all of the children turn out to be handicapped, they become angry with the fertility clinics. All sorts of difficult situations may occur: couples may lose one child and be left with one handicapped and one healthy child - 'a terrible cocktail' as one doctor put it.

Lieberman also raises the question of 'multifoetal pregnancy reduction' as it is euphemistically called. Women who conceive triplets are usually asked whether they would like to reduce the number of pregnancies.

'This is a horrific thing to do,' he says. 'It is awful. It can go wrong, you can lose all of them.' He approves of ordinary terminations when a woman does not want a baby but finds it 'unethical to create a pregnancy and then seek to terminate it'. Nor is it like other terminations, as the foetus must be left in place. Carrying live and dead babies next to each other can be, as one doctor put it with polite understatement, 'disconcerting'.

The villains of the piece, Lieberman makes clear, are the clinics in the private sector who want simply to 'get as many women pregnant as they can'. He does not attempt to hide his contempt for their irresponsibility. 'They do not have to deal with the premature babies that block scarce NHS resources.'

Lieberman estimates that it costs the taxpayer £40m or £50m a year to 'pick up triplets and twins from the private sector. This is more than the money spent on infertile couples by the NHS.'

Professor Alan Templeton, the RCOG's honorary secretary, regards this as a 'back of the envelope' calculation but says it is true that the cost of managing triplets in England is equivalent to the money spent on IVF. And he is clear about the way forward: 'We should be moving towards one embryo replacement.'

It takes a long time for Jacqui Bimson, from Quarry Bank in the West Midlands, to answer the phone. The first time, she doesn't make it. She heard it, she tells me later with cheerful resignation, but couldn't get to it. Her triplets - Jack, Sam and Thomas - are two and a half.

When I ask whether her children were the result of IVF, she says they were - but adds warily: 'Some people have the attitude that, you deserve everything you get. They assume you must be able to afford them, because you had all that expensive treatment.'

But triplets do not come cheap: you can pay £600 for a triple buggy, £90 for three pairs of shoes. Jacqui is at home by day and works at night, developing photographs, in order to afford her children.

There is no easy way of breaking the news to a woman that she is expecting triplets. One scanner's tactlessly jocular preamble was: 'Are you good at knitting?' Because of crossed wires between scanner and consultant, the Bimsons had not been told they were expecting triplets at all. The first they knew of it was when the consultant started ruminating about 'problems associated with multiple births'. Jacqui asked to have the word triplets written down on paper for her, before she could even begin to believe, let alone digest, the news.

In her autobiography, the sculptor Barbara Hepworth describes giving birth to triplets in the 1930s: 'I seemed withdrawn and concentrated over my pregnancy. But suddenly I said, "Oh dear," and in next to no time I saw three small children at the foot of my bed - looking pretty determined and fairly belligerent.' This sprightly fairy-tale is a little hard to believe. Hepworth was lucky: most triplets born in those days would not have survived at all.

Jacqui Bimson and her husband did not want to tempt providence by buying baby clothes. They hadn't got a Babygro in the house, they had never made up a bottle of milk.

'I found it hard to believe that any of my babies would live,' she says. 'We had lost two singletons very late on, one at 34 weeks, one at 28 weeks, so we didn't believe it until it happened.' Her triplets were born at 29 weeks; they were 'monster babies' (some weighed more than 3lb) given their prematurity.

'Jack did very well, he didn't need ventilation. Sam had a heart operation at three weeks old. We didn't think we would get even one baby home. Thomas was such a poorly little thing. But the nursing staff were always positive - even when we weren't.'

At five weeks, Jacqui Bimson's triplets came home. She and her husband sat them in a row in the lounge and said to each other: 'Life is never going to be the same again.'

They had almost no help from anyone, and none was offered by the state. It has been calculated that it takes 28 hours a day to look after triplets - tricky when there are only 24 hours available. The provision offered by the social services varies according to where you live - something Tamba hopes to regularise.

In one case, a woman with six-month-old triplets found she could not manage without help. She was exhausted and desperate and it was recommended that her children be taken into care. This was not only humiliating, it was senselessly cost-ineffective.

Jacqui Bimson was so tired she can hardly remember those early days. Looking at a photograph of a weekend she spent at her father's house, she has no recollection of being there at all.

In common with all the mothers of triplets I spoke to, she is keen that triplets should not be presented as an unqualified calamity. With enough help, 'triplets need not be a big problem'. Her advice to mothers (no mother of multiples would disagree) is: 'Accept all help you can. And buy a second washing machine and a dishwasher.' She also suggests that the house-proud or car-proud change their priorities. She loves her boys but she agrees with the guidelines that suggest that clinics replace only two embryos at a time. For anyone who thinks triplets are easy she has only this to say: 'I'll invite them round to my house for an afternoon...'

Mothers of 'super-twins' are - as if by definition - expected to be supermums. They have to be heroines, whether they like it or not. Jane Denton says, 'I do have concerns about this, they are put under enormous pressure to perform.' It is ironic that when it is hard for mothers to give triplets enough attention they should receive so much superficial attention from every passing stranger. But it is not surprising: from the outside, triplets have glamour, they are theatrical.

One mother told me that having triplets had made her understand what it was to become famous. Another said she felt as if she were a travelling circus. She found herself shouting: 'We're not a freak show!' She has lost count of the number of times she has been told 'rather you than me'. One couple counted the number of times their triple buggy was waylaid in Brent Cross shopping centre in London. They were stopped 72 times.

Sometimes, I was conscious of being on the receiving end of a performance. One mother spoke only of her elation about every aspect of her triplets. She was reluctant to admit that they could be challenging, until I asked if she agreed with the guidelines to limit the number of embryos replaced in a woman. To my surprise, she did. She said her body had been 'battered' by the pregnancy and mentioned 'post-natal depression'. She wanted to make light of it. In her case it had been 'mild', she said. She was 'on antidepressants for seven months'.

Fathers find it bewildering, too, when a 'ready-made' family arrives. Hugo Goodwin, a father of multiples, says: 'The invasion was such a shock. It is hard to focus on the new arrivals as individuals, hard to be certain about how evenly one can distribute one's attention and affection. The family itself feels contorted.'

The problem is partly that expectation does not always live up to reality. For mothers who have longed for children - and had a romantic idea of themselves as mothers - it can be painful (sometimes after more than a decade of fertility treatment) to admit to unhappiness, let alone to ask for help.

Joan Raphael-Leff is a psychoanalyst who has specialised in the effects on families - and mothers in particular - of reproductive technology and multiple pregnancy. She suggests that sometimes when the babies are born they seem disappointingly 'ordinary - or not so ordinary, smaller than average, requiring extra care'.

Raphael-Leff believes that the challenge of having multiple children begins antenatally. She has known women who have chosen to abort one or more of their triplets privately and then lied to their doctors at the fertility clinic, pretending that they miscarried. 'Clinics have an investment in the take-home baby. And there is still a romantic notion among some medical personnel that more is better.'

Women come for therapy, asking both 'Will my babies survive?' and 'What if they do?' They have sometimes 'a feeling of people inside you ganging up against you, you can't hide'. Then there is the further question: 'How do you bond and differentiate?' A mother may feel excluded. She may fear that the babies are 'closer to each other than to her' and there may be 'an assumption that because they can give to each other, the parents may feel that they need to give less, that the babies can occupy each other'. Raphael-Leff says it is 'very difficult to feel ordinary, to establish an ordinary family'.

Perhaps the best approach to having triplets is to accept this and salute the many ways in which it is extraordinary.

Janet Hanton, Tamba's Greater London co-ordinator for super-twins (her own triplets were conceived spontaneously), feels strongly that it is important for mothers of multiples to be able to talk to and support each other. She says triplets are 'a tremendous pleasure but an enormous strain. Some people say, "Triplets! How wonderful!" Others say, "You poor thing." It is both. But if I could, I wouldn't put back the clock.'

When I arrive, her three girls are undergoing potty training together. Even so, it seems like a small party is in progress. She loves watching her children: 'They have such a great time together. There is a special bond between them which I hope they will always have.'

Caroline, Katherine and Edward Halliday are robustly independent 22-year-olds. Although they are not IVF triplets, they are an encouraging model for families with young triplets. Caroline and Katherine are at Oxford, Edward has graduated from Edinburgh and is studying chartered accountancy. They convey an unidealised appreciation of each other. They are close but not oppressively so. Those who say 'Two is company, three's none' should think again. Caroline would like to overturn the assumption that triplets are all likely to behave in the same way. Katherine does not feel that they ever suffered from a want of individual attention. And Edward remembers the endless play.

Last wekk, I went to meet Judith Apter's charming four-year-old triplets. They were out in the garden with their watering cans and a hose. They are dark, bright-eyed, responsive.

Olivia rushed inside to show me a portrait she had drawn of herself, her brother and sister: three smiling faces in a row, like buttons. She was the pink one, I think. Chloë, at the same time, was telling me she detested the smell of mint, while Daniel told me he loved the taste of chives, shovelled fistfuls of herbs and unripe strawberries into his mouth and reeled off a recipe for cooking green pasta with parmesan.

I tried to respond to all three children at once. It was impossible. Olivia had the hose and - it was an accident, she promised - watered us all liberally. No one was cross but everyone was talking at once. Chloë rushed off to dry her new pink dress. 'Is pink your favourite colour?' I asked as she fled. 'It is!' she cried. 'But this is only one of my favourite dresses.' The conversation was like Daniel's chopped chives - or Olivia's hose - it went everywhere. I was struck by the simultaneity, the fun of it, the muddled miracle.

I hold on to the memory of that afternoon as an idyll - but know that idylls are fleeting and hard-won. Mothers of triplets cope because they have to cope. The Apters' children are a credit to them. But the IVF clinics are not accountable for anything that happens to the families they helped to create. If there is any moral to draw it is this: it is not fair to offer an infertile woman three wishes, unless she is sure that she wants them all granted.

IVF and infertility resources

Further reading

Three, Four and More; A Study of Triplet and Higher Order Births (HMSO) edited by Beverley J Bolting, Alison J Macfarlane, Frances V Price.

Useful contacts

The Multiple Birth Foundation 0208 748 4666

Tamba 0870 770 3305 or 01732 868 000

Online resources

The National Fertility Association and ivf-infertility.co.uk both offer information and links for couples who believe they might be infertile.