Birth Control Pills Still Linked to Breast Cancer, Study Finds

Pregnancy itself can cause death. See next post in my blog.

https://www.nytimes.com/2017/12/06/health/birth-control-breast-cancer-hormones.html

Women using birth control pills and I.U.D.s that release hormones face a higher risk than those using methods without hormones, scientists in Denmark reported.

By RONI CARYN RABINDEC. 6, 2017

Women who rely on birth control pills or contraceptive devices that release hormones face a small but significant increase in the risk for breast cancer, according to a large study published on Wednesday.

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The new paper estimated that for every 100,000 women, hormone contraceptive use causes an additional 13 breast cancer cases a year. That is, for every 100,000 women using hormonal birth control, there are 68 cases of breast cancer annually, compared with 55 cases a year among nonusers.

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The research also suggests that the hormone progestin — widely used in today’s birth control methods — may be raising breast cancer risk.

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Experts noted that oral contraceptives have some benefits as well, and are associated with reductions in ovarian, endometrial and possibly colorectal cancers later in life.

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The study also found that the risk increased the longer women used contraceptives involving hormones, suggesting the relationship is causal, Dr. Mørch said. “It is a very clear picture for us, very convincing.”

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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 I.U.D.’s, that contain the hormone progestin. (Not all I.U.D.’s release hormones.)

Women who used an intrauterine device that releases only progestin also faced a 21 percent increase in risk, compared with nonusers, the study found. The findings indicate that the hormone progestin is adding to breast cancer risk; some of the contraceptive pills and many of the I.U.D.’s included only progestin, Dr. Mørch said.

A 20 percent increase in relative risk may be small in absolute terms, but the calculation changes with age. For a 20-year-old woman, for example, the probability of developing breast cancer in the next 10 years is .06 percent, or 1 in 1,732, according to breastcancer.org.

Even if the relative risk increases 20 percent, it remains less than one-tenth of 1 percent. But by the time a woman reaches 40, her probability of developing breast cancer in the next 10 years is 1.45 percent, or 1 in 69. A 20 percent increase raises her risk to 1.74 percent, or 1 in 57.

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