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The longest clinical study ever conducted for a continuous-use birth-control pill has found that this new breed of the Pill is just as safe as traditional oral contraceptives. If it is approved by Health Canada, women will have the option of going period-free and never having to walk down the feminine hygiene product aisle again.

The study, financed by the drug's manufacturer, Wyeth Pharmaceuticals, bolsters chances of Health Canada approving the drug, Anya, which is not yet available in Canada or the United States. Results from clinical trials are crucial to a drug getting approved, along with data collected from trials in other countries.

Anya is the first birth control pill meant to be taken 365 days a year, without a monthly break to allow for menstruation. It would replace what many women already practise, which is throwing out the fourth week of dummy pills from their traditional oral contraceptives and going on to a fresh pack.

"In the past, my goodness, that was thought to be heresy to think you could do something like that," said Christine Derzko, an obstetrician and gynecologist from St. Michael's Hospital in Toronto, who has recommended the technique for years to patients who experience extreme discomfort with menstruation.

"But now we know it's thoroughly safe."

Results of the two-year Canadian study on Anya, presented yesterday at the Society of Obstetricians and Gynecologists of Canada annual clinical meeting in Vancouver, found that more than 80 per cent of the 79 participating women reported complete suppression of bleeding after two years of continuous use. Just over 5 per cent reported bleeding or spotting. And the low-dose pill was found to have the same risks associated with traditional oral contraceptives, according to researchers.

But this is just the latest ammunition for critics of menstrual suppression, who say there haven't been any assessments of long-term health risks, such as breast cancer and reduced bone density, done on women who take these contraceptives for an extended time. Health Canada and Wyeth are negotiating the possibility of following up every six months with women who take Anya to monitor any long-term side effects.

It's also just the latest endeavour in playing with a woman's monthly cycle.

Two years ago, Bar Laboratories in Pomona, N.Y., released a pill that tinkered with the traditional three-weeks-on, one-week-off formula established almost 50 years ago. It developed Seasonale, which is taken for 12 weeks straight, followed by a week of placebo pills, giving a woman only four periods a year. It had roughly $87-million (U.S.) in sales in 2004.

And for good reason, according to some.

Dr. Robert Reid, the lead investigator of the latest study, said that getting rid of the menstrual period also gets rid of the cramps, headaches and PMS that come with it. "The concern that you need to have menstrual bleeding for some reason is not based on any good science." Many advocates of menstrual suppression note that the roughly 1.5 million Canadian women on oral contraceptives don't even have a monthly period. The bleeding during the pill-free week is actually a "withdrawal bleed." There is no physiological need for it, Dr. Derzko said.

"For some women, it's just the nuisance of having bleeding when you don't want to, but for others it can be very serious medical [side effects]."

But it's precisely this tendency to focus only on the bleeding portion of the cycle that bothers some critics of menstrual suppression.

"Extended and continuous cycles of oral contraceptives maintain hormonal stimulation at higher than physiological levels for a longer time," said Dr. Christine Hitchcock, a research associate at the Centre for Menstrual Cycle and Ovulation Research at the University of British Columbia. "It is this lack of a break from hormonal stimulation that is potentially a problem, not the lack of menstrual bleeding, that occurs during the pill-free interval."

Dr. Hitchcock said the problem with studies looking at the safety of oral contraceptives always compare results to women on other forms of oral contraception --"they haven't seen if this is better than doing nothing at all"-- and she's concerned about the long-term health risks that can come with constantly being on a high dosage of hormones, usually four to five times higher than what the body naturally produces.

"They say that [oral contraceptives] reduce ovarian cancer, but what they don't tell you is that it increases cervical cancer," she said. "And still, nobody's looked at the effects on breasts, nobody's looked at the effects on teenage development, breast density, bone density."

She referred to a 25-year study of 45,000 British women (half on the Pill, half not) that found deaths from cancer of the cervix and from cardiovascular diseases were significantly increased in women on oral contraceptives.