A new study has found that birth control pills and injectable contraceptives may raise breast cancer risks and lower risks for ovarian cancer. The study reviewed women’s use of both injectable and oral birth control methods.
While users of these types of contraceptives were at a significantly lowered risks for ovarian cancer, they were at a significantly increased relative risk of developing invasive breast cancer, said ABC News. The study was based on a review of black women in South Africa. Risks decreased as time passed after the contraceptives were ceased. The study appears in PLoS Medicine.
Data was self-reported by 5,702 participants who were newly diagnosed with invasive breast, cervical, ovarian, or endometrial cancers, said ABC News; 1,492 women served as controls and were diagnosed with other cancers such as colon, rectal, and non-Hodgkin lymphoma, which are not affected by contraceptives. Of the participants, 26% used injectable hormones and 20 used pills.
After adjustments were made for so-called “confounding factors” such as age, education, smoking, and the number of sexual partners, the researchers found that women were 1.7 times likelier to develop breast cancer and 1.4 times likelier to develop cervical cancer, versus women never took the contraceptives, ABC News said. About half of the women with breast cancer, 26% of the women with ovarian cancer, and 17% of the women with endometrial cancer had used the contraceptives.
Injectable contraceptives are a common form of birth control by black women in South Africa, the authors noted; in the U.S., birth control pills are more typically used by women, said ABC News. Combined injectables provide monthly hormones to prevent pregnancy, which is similar to how oral contraceptives work. Hormones are some of the most popularly prescribed and taken medications in the world with about 9% of women 15-49 taking oral contraceptives and 4% using injectable contraceptives or implants in 2007, according to a 2009 United Nations report, said ABC News.
Oral contraceptives have been linked to other health problems. For example, a U.S. Food & Drug Administration (FDA) study found that women taking Yaz, Yasmin, and similar new-generation birth control pills made with drospirenone may have a 75% greater chance of experiencing a Venous thromboembolism (VTE) compared to women on other pills. The FDA study involved an examination of health records belonging to 800,000 American women using some sort of birth control
The results of the FDA study were released just days after a publication of a Danish study which found that oral contraceptives with new-generation progestins, including drospirenone, doubled the risk of VTE versus pills made with an older form of progestin called levonorgestral. Not all studies have found increased risks with drospirenone.
In December, an FDA advisory panel recommended that stronger blood clot warnings be added to the labels of Yaz, Yasmin and other birth control pills that contain drospirenenone, after finding current warnings are inadequate.