Birth control can increase a woman’s risk of breast cancer by up to 1.38-times, depending on how long she has take it. The risk is associated with all forms of hormonal contraception – such as the pill, injections, or IUDs – when compared with women who have never used them.

Researchers from the University of Copenhagen analyzed data from 1.8 million women under the age of 50 in Denmark. They followed the women for nearly 11 years,on average. The level of risk increased the longer a woman had been taking hormonal contraceptives, with the average risk 1.2x greater among all current and recent users. Among those taking hormonal contraceptives for under a year, the risk increased by 1.09x, compared to 1.38x for those on them for more than 10 years. Among women who had been using hormonal contraceptives for more than five years, a slight risk persisted for at least five years after they stopped.

My Take: We have long known of the increased risk of breast cancer associated with the taking of oral contraceptives. Now we have data looking at newer preparations of contraceptives. These results suggest that no hormonal type of contraceptive is risk-free. However, breast cancer is relatively uncommon among younger women. For those under 35 in this study, taking contraceptives for less than one year resulted in 1 extra case per 50,000 women. Rates are five times higher in women in their 40s (when compared to those in their 30s), and women in the higher risk category may wish to discuss non-hormonal options with their health care provider.

Finally, for the overall group of women, risk declines over time after stopping the medicines. In addition, I would note that oral contraceptives may lower a woman’s risk of ovarian, endometrial, and colorectal cancers later in life. In addition, while the risk of breast cancer was higher among women who currently or recently used contemporary hormonal contraceptives (with risk increasing with duration of use), the absolute increases in risk were small. I’m Dr. Michael Hunter. If you want to learn more, please hit the Wellness! Button on the top left of this page. And to follow the blog, head to the comments section, and sign up. Thank you!