However, there is one warning: Women who take the pill longer than eight years do have an increased risk of cancer.

Since its introduction in the early 1960s, more than 300 million women are thought to have used oral contraception. Although several studies have looked at the overall balance of cancer deaths associated with oral contraceptives, until now none have examined the absolute risks or benefits.

The study: Led by Philip Hannaford, the University of Aberdeen team analyzed data from a 36-year study that began in 1968 with 46,000 women with an average age of 29. Half of the participants were using oral contraceptives, while the other half never took them. Every six months for 36 years, each woman's doctor notified the study leaders about the woman's health. The researchers used the data to calculate the risk of developing any type of cancer, as well as the main types of gynecological cancers. They also considered the effects of variables such as age, smoking and social class.

The results: The researchers determined there is no overall increased risk of cancer among pill users. In addition, women who took the pill for at least a year at any point in their life had as much as a 12 percent reduced risk of developing any type of cancer--the equivalent of one fewer cancer case for every 2,200 women. Among those who took birth control pills there was a statistically significant lower rate of large bowel/rectal, uterine body and ovarian cancer.

But beware! Women who used the pill for more than eight years had a statistically significant increased risk of developing any cancer, in particular cervical and central nervous system cancer. However the same women were at a reduced risk of developing ovarian cancer. Evidence suggests that the protective effect of taking the pill lasts for at least 15 years after stopping use.