In 2003 a study from England showed that the longer a woman takes birth control pills, the greater her risk of developing cervical cancer. The researchers reviewed 28 studies and found that compared to women who never took "the Pill," those who were on it for less than five years had a 10 percent increased risk of cervical cancer; those who took it for five to nine years had a 60 percent increased risk and those who took it for 10 years or more had double the risk.
Even after accounting for such risk factors as the number of sexual partners the women had, their smoking history (cigarettes raise the risk) and infection with the human papillomavirus (HPV), believed to be the major cause of cervical cancer, the researchers found that the length of time on the Pill correlated with an increased risk of cervical cancer.
However, even double the risk isn't as scary as it sounds since cervical cancer isn't very common these days. In the UK only 3,200 cases occur annually. In the U.S., some 12,000 women develop cervical cancer every year, most of whom have not been screened as recommended with regular Pap tests.
The study doesn't reveal what it is about the Pill that could be responsible for the increased risk, but we do know that the risk returns to normal 10 years after a woman stops taking the Pill. We also know that long-term use of birth control pills protects against ovarian cancer, a far worse and much less treatable disease. Fortunately, Pap smears can detect early indications of cervical cancer making it possible to prevent progression to the disease itself. In addition, in 2006 the FDA approved the vaccine Gardisil, which protects against the two strains of the human papillomavirus (HPV), which are responsible for 70 percent of all cases of cervical cancer.
I wouldn't base a decision on whether or not to continue taking the Pill solely on the results of the British study. That's a decision you should make after consultation with your physician, taking into consideration your lifestyle and personal and family health history. But I would also encourage you to learn about non-pharmacological approaches to birth-control. If you can find a method that works for you, it might be safer than long-term use of the Pill.
Andrew Weil, M.D.