Study Finds Link Between Birth Control and Breast Cancer


Newer formulations of birth control pills appear the carry the same risk of breast cancer as older versions.

Researchers in Denmark analyzed data on 1.8 million women and found that using any type of hormonal contraceptive was linked to a 20-percent higher risk of breast cancer.

However, the absolute risk for developing breast cancer for most women is extremely low. Another way of looking at that is that there would be one additional case of breast cancer each year among 7,700 people who use hormonal contraceptives.

What really surprised the researchers was that the increased risk was not confined to women using oral contraceptive pills, but also was seen in women using implanted intrauterine devices, or IUDs, that contain the hormone progestin.

There are also numerous potential health benefits of hormonal contraceptives beyond preventing pregnancy, including decreasing the risk of endometrial, ovarian and colorectal cancers, as well as helping with menstrual cycle regularity, migraines and acne. And for those who take the drugs for five years or more, the risk will persist for as long as five years after they stop, she said.

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The study also found that the risk increased the longer women used contraceptives involving hormones, suggesting the relationship is causal, Mørch said. For starters, a lot more research needs to be done on the long-term effects of all types of birth control.

But by using computer databases from national health systems, which in Denmark are comprehensive, researchers can look at years of patient data far more cheaply, and with no risk of losing contact.

NEIGHMOND: All of these forms of hormonal contraception increased breast cancer risk by 20 percent.

The idea that there is a link between hormonal contraceptive use and breast cancer is not new. They compared what happened over almost 11 years among women taking hormonal birth control and women using other methods. Mia Gaudet with the American Cancer Society says the findings are compelling because researchers didn't just look at the birth control pill. However, it was commonly thought that the newer low-dose estrogen options significantly decreased - or even eliminated - that risk. But that's not what this study found. "But we should make an individual assessment-doctor and a woman, together-to see what is the most appropriate thing for her to use". For a 20-year-old woman, for example, the probability of developing breast cancer in the next 10 years is 0.06 per cent, or 1 in 1,732, according to And if it's not needed to take hormonal contraceptions, it might be worth considering using other methods like the copper IUD or barium if it's - like condoms, for instance. Age, family history and weight gain later in life all contribute to breast cancer risk.

NEIGHMOND: Now, it's important to note in the study, women over 40 were more likely to suffer breast cancer than younger women in their 20s and 30s. And so many calculations suggest that use of all contraceptives actually prevents more cancers than it causes.