Women who use a certain type of long-acting hormonal contraceptive are at a slightly increased risk of broken bones, new research suggests.
More than 9 million women worldwide use Depo Provera, an injection of progesterone given every three months, Dr. Christoph R. Meier of University Hospital Basel in Switzerland and his colleagues explain in the Journal of Clinical Endocrinology and Metabolism. Some evidence has suggested that the contraceptive, which suppresses estrogen production, could weaken bones, but it's not clear whether the drug actually increases the risk of bone fractures, the authors add.
To investigate, Meier and his team compared 17,527 women 20 to 44 years old who were diagnosed with a fracture between 1995 and 2008 to a control group of 70,130 women in the same age range who were fracture-free.
Depo Provera was linked to an increased likelihood of fractures, the researchers found; women who were currently using the contraceptive and had filled one or two prescriptions had an 18 percent greater likelihood of fractures than nonusers.
Women with three to nine prescriptions were at 36 percent increased risk, and women with 10 or more prescriptions were at 54 percent increased risk. The greatest increase in risk was seen among current Depo Provera users who had been using the contraceptive for more than two or three years.
Among women who had not used Depo Provera for the past 720 days or longer, fracture risk associated with the contraceptive "largely disappeared," Meier and his colleagues note, suggesting that women may recover lost bone mineral density once they stop using the drug.
While there have been few studies on the risk of fractures among premenopausal women, one study of 17,000 women done in the United Kingdom found that 1,300, or about 8 percent, sustained fractures during 26 years of follow-up. Based on this figure, and the new findings, a woman using Depo Provera for at least 30 months would have a 12 percent likelihood of breaking a bone over the next couple of decades.
In 2004, the U.S. Food and Drug Administration and Pfizer, the company that makes Depo Provera, added a warning to the drug's labeling stating that use of the contraceptive can lead to loss of calcium in the bones, and that greater loss occurs with longer use. The label advises women against using the drug for longer than two years, stating that they should do so "only if other birth control methods are inadequate."
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