It has been taken by hundreds of millions of women and hailed as one of the most significant inventions of the 20th century. Now prepare for the latest revolution in the Pill - a "lifestyle" oral contraceptive that limits periods to just four a year.
The new pill, called Seasonale, has just been approved by the US Food and Drug Administration, with California-based Barr Laboratories Inc due to market it throughout America. It is expected in Britain next year. By limiting periods to only once a season, Seasonale claims to dramatically improve the life of career women. It was broadly welcomed by medical experts yesterday although some warned it could multiply the current risks of taking the Pill - including breast cancer and even deep-vein thrombosis. Its makers claimed it would actually reduce the risk of ovarian cancer. Seasonale combines two hormones commonly used in oral contraceptives, but extends a woman's cycle to three months - meaning it must be taken for 84 consecutive days instead of the usual 21. By limiting periods, the manufacturers claim it can reduce the symptoms of menstruation, such as cramps and pre-menstrual tension (PMS).
Contraception and the Pill in particular are big business. The market for hormone-based contraceptives is now worth £2.3bn a year worldwide, and pharmaceutical giants are desperate to claim their share. The good news for women is that a whole new generation of contraceptives will be available by the end of next year. By the time Seasonale comes to the UK, it is expected to face competition from a range of hormone-based drugs - targeted at career women.
These include the NuvaRing, a flexible ring inserted into the vagina that releases a dose of combined hormones for several weeks at a time. Another is Lunelle, a hormone injection, while a third is already licensed to market a special hormone patch in the UK called Ortho-Evra.
Scientists are currently working on advanced "smart" hormones, which could be used in gels and inhalers and ultimately replace oral contraceptives. Until all these new products become available, however, the Pill remains the most popular reversible contraceptive in the UK. First developed by Carl Djerassi in 1951, it works by artificially raising the level of female hormones in the blood. This prevents the shredding of the lining of the uterus - the bleeding seen during menstruation. But Djerassi and his team failed to realise that most women would prefer not to have a monthly bleed. He thought women would be reassured by the fact they still bled every month. A recent study of 1,000 women by the Department of International Development and the Medical Research Council found that the majority of women wanted an end to their period.
Carol Cox, spokeswoman for Barr Laboratories, said: "It's for women who want the convenience of only four periods a year. These days women start their periods younger and end older. Studies have shown this can increase the risk of ovarian cancer." One of Britain's leading experts on the subject, and author of The Pill, Prof John Guillebaud said: "You would just get a period in spring, summer, autumn and winter ... It would mean taking more hormones than before." Prof Guillebaud said it would benefit women who suffer from endometriosis - the painful condition where fragments of the womb lining break off and find their way into other parts of the reproductive system.
Marilyn Monroe is understood to have suffered from the condition, which currently afflicts some two million British women. Dr Deborah Beere, a leading consultant in contraception and reproductive health, said Seasonale would just legitimise a practice used by doctors called "tricycling". This involves the taking of three packs of pills together, so women do not have a bleed if they are taking exams or going on holiday. Dr Beere said: "It's important that women look at all the options available before they make a decision." While praising the choice offered by Seasonale, Dr Peter Bowen-Simpkins, of the Royal College of Obstetricians and Gynaecologists, sounded a warning note. He said: "It does mean ingesting more hormones. Theoretically, this could increase the risk of breast cancer and deep-vein thrombosis. There is also a danger of breakthrough bleeding the longer you delay menstruation," he said. The agony aunt Virginia Ironside, who has been advising women for decades, said: "This is a very interesting step forward. The next big revolution is going to be the male pill. Now I can't wait to see what happens with that."
'At its peak, it was so bad I couldn't go into work'
Penny Tranter was 18 when she first noticed a problem with her periods. At university, she was told the intense stomach pains she was experiencing were due to exam pressure and nerves. In fact they were something much more serious.
Seven years later, Penny was finally diagnosed with the crippling gynaecological condition endometriosis.
Sufferers experience severe abdominal pain and heavy periods and sex is often painful. Penny, a BBC weather presenter and 42-year-old mother-of-two, says she would welcome a product like Seasonale, which could alleviate the symptoms and help women like her to lead more normal lives. "For me, when it was at its peak, it was so bad that I couldn't go into work," she says. "Periods are heavy and sex is painful. It also made me very tired and depressed - it's an awful condition."
Penny, who lives near Bath and is married to Martyn, a university lecturer, says Seasonale sounds an "ideal" option for women like her.
"From my own personal point of view, Seasonale would be fantastic," says Penny. "Anything that can help with endometriosis is good and should be applauded. By the time most women discover it, they are experiencing serious pain."
The Pill: a history of oral contraception
1951: Carl Djerassi synthesises first oral contraceptive. He later becomes known as "the father of the pill".
1960: United States Food and Drug Administration (FDA) approves oral contraceptives for marketing.
1961: Pill goes on sale in UK for first time. Ministry of Health decides to offer it on NHS. Concernsthat Pill might predispose some women to heart attack and stroke. Evidence of blood-clotting also reported.
1966: FDA advisory body reports "no adequate scientific data to prove the Pill unsafe for human use". Becomes leading method of contraception in US.
1969: Research reveals that the risks of blood clot, heart attack and stroke are directly related to level of oestrogen in the Pill.
1970: FDA advises doctors to use lowest dose of oestrogen possible. "Mini-Pill", containing only progestin, is introduced.
1982: New "multiphasic" Pills are introduced, in which ratio of progestin to oestrogen changes during the 21 days Pill is taken.
1988: Several potential non-contraceptive health benefits of Pill are recognised, including decreased incidence of ovarian cancer.
1998: Pill approved for use in healthy, non-smoking women over 40.
1999: Oral contraceptives legalised in Japan, along with Viagra.
2003: Trials of male contraceptive in form of implants and injections prove 100 per cent effective, clearing the way for male oral contraceptive pill.