A new type of contraceptive promises to free women from the hassle of monthly periods. It may offer health benefits, too. But some say it's a triumph of lifestyle marketing over good medicine. Catherine Nixey reports

The 1970s feminist might have tasted her own menstrual blood but the millennial feminist doesn't even want to look at hers. "This term we have 12 exams in eight weeks," says Ruth Evans, a 21-year-old veterinary student at Cambridge University. "I have to work from nine in the morning till 10 or 11 at night every day; which leaves you constantly exhausted. The last thing I want on top of that is the pain, tiredness and mess of a period."

But for Ruth and many women like her an end to the monthly misery of menstruation may well be in sight. A "lifestyle" contraceptive pill called Seasonale, which limits women's periods to just four a year, was launched in the United States in 2003 and is expected to arrive in Britain later this year. Women will take Seasonale for 84 consecutive days instead of the usual 21 of the standard contraceptive Pill, and so will only bleed once every three months. Barr Laboratories, the American drugs company that manufactures Seasonale, claims that by removing the need for a monthly bleed, the pill will improve the lives of career women.

"It is for women who want the convenience of only four periods a year," a spokeswoman for the company says. Women such as Ruth. "I'd definitely take it," she says. "I'd love to have four periods a year... In fact, I'd love to have no periods a year. They just get in the way. So if you can get rid of them safely - well, why not?"

"We welcome it," says Melissa Dear of the Family Planning Association. "We welcome anything that extends the range of contraceptive choice available to women. Many women might find a period troublesome - either because they have painful, difficult periods, or perhaps simply because at certain times in their life, such as when they go on holiday or have exams, periods are inconvenient."

Such "lifestyle" marketing demonstrates how much attitudes to the Pill have changed. When it first went on sale in this country in 1961, the synthetic regulation of a woman's menstrual cycle was a fairly alien and alarming concept. The combined Pill works by containing two hormones, oestrogen and progestogen, which mimic the hormonal balance of pregnancy, so suppressing ovulation, hence making fertilisation impossible. The present format of the Pill - 21 days of hormones followed by seven days off - was decided on not out of the medical necessity of mimicking the menstrual cycle, but because it was felt it would act as a sop to women's anxiety.

Surveys in the Seventies confirmed that belief, indicating that women were not only reassured by monthly bleeding but that they even liked it, feeling that it indicated femininity and normality, and fertility without pregnancy.

Since then, however, the Pill has gone on to become the most popular reversible form of contraception in the UK, used by over 3.5 million women. As women have become more familiar with the Pill, attitudes have changed: women are now much more comfortable with the idea of manipulating their bodies' menstrual cycles with drugs.

A survey conducted last year showed that about two thirds of women would prefer to bleed less frequently - with one third of these saying that they would rather not bleed at all.

But the attitude of the manufacturers has remained unchanged: the same survey found that 80 per cent of them still thought that regular menstruation was either quite important or very important to their clients. "We certainly know that a significant number of women would welcome an end to their monthly period," says Melissa Dear. "It's amazing that it's taken so long for the drug companies to catch on."

But Professor Carl Djerassi, the inventor of the Pill, is not: "It is purely a question of marketing. Until now, none of the principal manufacturers of the Pill has chosen to market this sort of extended Pill, and it is likely to remain a niche market. But if it does catch on, then I am sure that the giants in the field will follow suit."

The concept of taking the Pill without a break to avoid the monthly period is not a new one; doctors have long adopted a process called tricycling (pronounced "tri-cycling") for women who suffer seriously from headaches or bad PMS during the Pill-free week. In this process, three packets of pills are run together, thus avoiding bleeding for 62 days. Seasonale, which contains the same hormones as the normal combined Pill and works in the same way, is simply an extension of this process. So what is so special about it?

"Nothing at all," says Peter Bowen-Simpkins of the Royal College of Obstetricians and Gynaecologists. "This practice has been around for years and years and we have been practising it. All this company has done is to put four months' worth of pills into one single packet. This is a repackaging exercise, nothing else."

But despite its long history, many women who might have benefited from this practice have still never heard of it. So the FPA's Melissa Dear is still enthusiastic: "Although there always was the option that women could tricycle the normal Pill, Seasonale will help to give women and GPs the confidence to do so."

And the presentation of the contraceptive pill is by no means irrelevant to its success. "It could help to prevent more unplanned pregnancies," says Melissa Dear. "Many of the unplanned pregnancies associated with the regular Pill centre around the seven-day break - after they stop taking the pill women often forget to start taking it again, or start a day late."

"When you ask women when the most dangerous time to forget a pill is, they will say in the middle of the month, but it isn't," says Bowen-Simpkins. "The most dangerous time in terms of pill taking is to forget to take pills at the beginning of a new packet: in other words to extend the pill-free week. The longer you extend it the more dangerous it gets. So, of course if you are taking one of these prolonged cycles then this will remove some of that risk and that is a very positive thing."

Numerous other benefits have been mentioned - it will hugely benefit women who suffer from painful complications of bleeding such as endometriosis. And in their circumspect statement that "These days women start their periods younger and end older. Studies have shown that this can increase the risk of ovarian cancer," Barr raise the idea that the increased period-free time could help to decrease the risk of at least one type of cancer.

Some rather erroneous benefits have been suggested as well. One British newspaper (whose blushes we shall spare) wrote that "It is also thought that Season-ale could help women stay fertile for longer because only four eggs would be released from the ovaries each year, rather than 12."

"That," says Bowen-Simpkins, "is complete and utter rubbish. It could not be more wrong." The reason it is wrong is that even if you ovulated at all whilst on the Pill [you don't], and even if infertility in women was caused just by loss of eggs through ovulation [it isn't], then each woman has so many eggs in her ovaries that she would have to reach the ripe old age of 2,500 before infertility struck."

And although it may initially seem unnatural, prolonged amenorrhoea is actually nothing new. An article in the Medical Bulletin of the International Planned Parenthood Federation last summer said "regular menstruation is not 'natural': before modern contraception, women spent much of their reproductive lives amenorrhoeic as a consequence of either pregnancy or breastfeeding".

But there are risks attached with all medicines, and Seasonale is no exception. After numerous highly publicised health scares it is well known that the Pill causes increased risk of breast and cervix cancer and thrombo-embolism (the formation of blood clots in arteries and veins). However, it is now also well known that the risks of these are low enough that the Pill is, for most women, medically "safe".

But there are, nevertheless, risks associated with hormone ingestion. And because Seasonale is taken for an increased period of time - 48 weeks a year as opposed to 39, an increase of 25 per cent - you are proportionately increasing the amount of hormones ingested.

And it remains to be seen how Seasonale will be publicly received: as a liberation from periods, or as an unnecessary and unnatural constraint on the natural processes of women - another hair plucked from the bikini line of femininity.

So far, however, it is being welcomed by doctors, health workers and women alike. As the woman who did more than anyone else to bring menstruation out of the water closet, the last word should perhaps rest with the prescient feminist writer and broadcaster Germaine Greer.

As she wrote more than three decades ago in her most famous work, The Female Eunuch, "Why should women not resent an inconvenience which causes tension before, after and during; unpleasantness, odour, staining [and] which takes up anything from a seventh to a fifth of her adult life until the menopause? The fact is that no woman would menstruate if she did not have to."