In the largest study of its kind, researchers in Denmark have found that the risk for myocardial infarction (MI) and thrombotic stroke is doubled for women who use combined estrogen-progestin contraceptives.1 However, the overall risk of a patient experiencing either adverse effect is low, according to the study findings. News headlines discussing the study tended to overstate the risk, and patients may have new concerns about the safety of their hormonal contraceptive
This 15-year study assessed the risk of arterial clots in women aged 15 to 49 years who used hormonal contraception. More than 1.6 million women were included in the study, with approximately 14.2 million person-years observed. Researchers noted 3311 cases of thrombotic stroke and 1725 cases of MI.
Compared with women not using hormonal contraceptives, women using birth control pills were 1.5 to 2.0 times more likely to have an MI or a thrombotic stroke. In women using vaginal rings and transdermal patches, the risk of an MI or stroke was 2.5 to 3.0 times greater. Hormonal contraceptives containing 30 to 40 micrograms of ethinyl estradiol(Drug information on estradiol) were associated with a greater risk of MI and stroke than those containing 20 micrograms of the hormone (1.3 to 2.3 vs 0.9 to 1.7, respectively).
These findings confirm what is already known about hormonal contraceptives and essentially refine the estimated risks associated with various combinations of hormones in contraception. Understanding how these findings translate to clinical practice is essential for optimizing patient safety. The older a woman is, the greater her risk for a clot-based complication, says Ojvind Lidegaard, MD, lead author of the study. “A doubled risk for thrombotic stroke is not very serious when you are 20 years old, because your risk at baseline is very low. On the other hand, when you are 35 years old or older, the risk is no longer that low, and you should be more careful with choosing those products with the lowest risk of thrombotic complications.”2
The most intriguing finding, according to Diana Petitti, MD, MPH, was that the safety profiles of all contraceptives containing progestin, despite the various formulations of the hormone, were similar.2 “Decision making should focus more on effectiveness and adherence and not on miniscule differences in the potential for vascular disease. All of the current products on the market are safe enough,” says Petitti.
- The absolute risk for myocardial infarction or thrombotic stroke associated with use of hormonal contraceptives is low.
- Women with high blood pressure and diabetes and those who are older than 35 years are at significantly greater risk for MI and stroke from use of estrogen-progestin contraceptives.