Many women use various forms of contraception to prevent unwanted pregnancies. Like numerous medications and devices, some forms of birth control carry risks of side effects. Potential side effects may differ depending on the type of contraception, mainly oral versus non-oral birth control, and some types of side effects are much more severe than others. In fact, according to a recent Danish study published May 10, 2012 in the British Journal of Medicine (BJM), women using non-oral contraception may have an increased risk of developing dangerous blood clots, like deep vein thrombosis (DVT).
DVT is a blood clot that forms in deep veins, often in the calf or thigh. The clot can travel through the bloodstream to the lungs, heart or brain (called an embolism). Some common symptoms of blood clots may include shortness of breath, leg or chest pain. Serious blood clots can cause heart attack, stroke or even death.
Study Findings and Increased Risk for Women
The study was led by Professor Øjvind Lidegaard of the University of Copenhagen and followed non-pregnant Danish women ages 15-49 from January 1, 2001 to December 31, 2010. Women who had cancer or previous instances of DVT were omitted from the study and factors that could impact results, like age or education level, were taken into consideration. Studies have been done in the past on the risk of blood clots with oral birth control use, but the Danish study was focused on non-oral contraception, such as the vaginal ring (NuvaRing), skin patches (Ortho Evra) and vaginal implants (intrauterine devices or IUDs).
Study findings showed that women using non-oral contraception during the ten-year period had an increased risk of developing blood clots that was 2 times greater than women using oral birth control pills containing levonorgestrel (sometimes referred to as second-generation birth control pills). Additional findings from the BJM published study include:
- 6.2 incidents of blood clots per 10,000 exposure years for women using oral birth control pills (containing levonorgestrel)
- 7.8 incidents of blood clots per 10,000 exposure years for women using a vaginal ring (NuvaRing)
- 9.7 incidents of blood clots per 10,000 exposure years for women using the contraceptive patch (Ortho Evra)
Interestingly, the study also found that women using a progestogen containing intrauterine device did not have an increased risk of developing dangerous blood clots.
Based on the 10-year review of non-oral contraception users, researchers concluded that women using vaginal rings or the contraceptive patch have a 6.5 and 7.9 increased risk of developing dangerous blood clots as women who do not use these types of contraception. Due to the seriousness venous thrombosis, authors of the study recommend that women use oral contraception as a birth control method and consider discontinuing non-oral birth control use.