Figure: Certified nurse midwife Gwen Riddell administers the injectable contraceptive DMPA to a patient at the Southwest Community Health Center in Santa Rosa, California. Photo © ZUMA Press / Newscom.

Women of childbearing age have a multitude of options when choosing hormonal contraceptives, many of which contain the hormone progesterone, or progestin, or its synthetic versions. Growing concern over the risks associated with some progestin-based contraceptives has prompted the Food and Drug Administration (FDA) to require a drug-label change.

Based on a review of observational studies, the FDA concluded in April that birth control pills containing the synthetic progestin drospirenone may be associated with a higher risk of blood clots—according to some studies, as much as a threefold higher risk—than pills containing levonorgestrel. The pills at issue are sold under a variety of brand names—Yaz, Yasmin, Safyral, and Beyaz—and the drugs' labels will be revised to provide information on the studies. But the FDA safety warning notes that some studies found no increased blood clot risk, and in those that did, patient characteristics that might affect the risk of clots often weren't controlled for.

The FDA warning suggests that women discuss this risk, as well as the benefits of these pills, with their health care providers before deciding on a birth control method. To read the FDA Drug Safety Communication, go to http://1.usa.gov/Hyl1tu. It's also worth noting that a recent Danish study, published online May 10 in BMJ, found a higher risk of blood clots in women using either a transdermal contraception patch or a vaginal ring than in women using oral contraceptives (estrogen with levonorgestrel).

Blood clots aren't the only health concern to consider when choosing birth control. A recent study also found that the injectable contraceptive depo-medroxyprogesterone acetate (DMPA) was associated with an increased risk of invasive breast cancer.

DMPA contains the same progestin used in the hormone therapy regimen found to increase breast cancer risk among postmenopausal women in the Women's Health Initiative clinical trials, yet its use has been on the rise since its approval as an injected contraceptive in 1992.

Noting the limited data on DMPA use and breast cancer, researchers conducted a population-based case–control study of 1,028 women 20 to 44 years of age to examine the risk. The subjects, all of whom were diagnosed between June 2004 and June 2010 with a primary invasive breast cancer and had had no history of the disease, were questioned about DMPA use. Recent users of the injectable contraceptive who had taken it for 12 months or more had a 2.2-fold increased risk of breast cancer. However, former users (women who had stopped taking it more than five years before) showed no increase in risk, nor did recent users taking it for less than 12 months.

Writing in the April 15 issue of Cancer Research, the authors note that although the risk of breast cancer in premenopausal women remains low, health care providers should clarify the benefits and risks associated with birth control methods so their patients can make the best possible choice.—Laura Wallis