Does using the contraceptive pill increase my risk of cancer?

Ovarian cancer and uterine cancer are demonstrably less likely in pill users. The risk of ovarian cancer falls by around 40%, and this protective effect persists for years after stopping. Something similar applies to uterine cancer: the progestogen component in the pill suppresses cell growth in the uterine lining, and this benefit also remains after stopping.

For breast cancer the picture is more nuanced. For the average user, research covering more than 72,000 cases shows no significantly elevated risk. However, two subgroups deserve attention: women who use the pill before their first full-term pregnancy, and women who take the pill for longer than five years. In both groups the relative risk is approximately 9 to 14% higher than in non-users. That sounds alarming, but because young women already have a low baseline risk of breast cancer, the absolute extra risk is very small in numerical terms.

Current or recent use (within the past ten years) also appears to cause breast cancer that was already developing to become detectable slightly earlier. The pill probably does not create new cancer cells, but may cause cancer cells that are already present to grow a little faster. The tumours found in pill users are generally less advanced than those found in non-users. The elevated risk gradually decreases after stopping.

For cervical cancer there are indications that long-term use slightly raises the risk. However, pill users are also more frequently exposed to the HPV virus, due to a combination of behavioural factors such as reduced condom use. The pill appears to enhance the effect of HPV, but is not itself a direct cause. Regular cervical smear tests remain just as important. Whether a direct biological link exists has not yet been definitively established.