PCOS Increases Risk of Venous Thromboembolism for Women on Oral Contraceptives

Women with polycystic ovary syndrome (PCOS) who take combined oral contraceptives are more than twice as likely as women without PCOS who take oral contraceptives to have a venous thromboembolism (VTE), according to the findings of a new study.¹

It has been well established that women who take oral contraceptives have an increased risk for VTE. What has been unknown is whether women with PCOS have an additional increased risk for VTE. To better understand the association between PCOS and risk for VTE in women who take oral contraceptives, researchers from the United States and Canada developed a population based cohort using data from a large claims database. They identified 43,506 women aged 18 to 46 years who were taking combined oral contraceptives and who also had a claim for PCOS. These women were then matched to 43,506 control women who were taking oral contraceptives but who did not have PCOS. Women with a history of cardiovascular disease, cancer, and blood clots were excluded from the study.

Compared with women without PCOS who used combined oral contraceptives, the relative risk for VTE of women with PCOS who took combined oral contraceptives was 2.14. In addition, researchers found that the incidence of VTE in women with PCOS was 23.7 per 10,000 person-years, compared with 10.9 per 10,000 person-years for matched controls.

Interestingly, when researchers analyzed the data related to women with PCOS who were not taking combined oral contraceptives and made comparisons with data from women without PCOS who were not taking oral contraceptives, they found that women with PCOS were still 1.5 times more likely than their matched controls to have a VTE. In this subgroup, the incidence of VTE dropped to 6.3 per 10,000 person-years. In matched controls, the incidence of VTE was 4.1 per 10,000 person-years.

Combined oral contraceptives, which can increase risk of cardiovascular events, are often prescribed to women with PCOS to help regulate menstrual cycles, control acne, and minimize excessive hair growth. However, women with PCOS already are twice as likely as women without PCOS to have heart disease, diabetes, and obesity. Some have speculated that oral contraceptives might protect against any increased risk for VTE that PCOS may predispose women to, especially in women aged 18 to 24 years.² However, these findings suggest that combined oral contraceptives further increases the risk of VTE in women with PCOS.¹

Pertinent Points:
- Compared with women without PCOS who take combined oral contraceptives, women with PCOS who take oral contraceptives have more than double the risk for a blood clot.
- Physicians should consider this additional increased risk for venous thromboembolism when prescribing combined oral contraceptives to women with PCOS, conclude the study authors.

References:

1. Bird ST, Hartzema AG, Brophy JM, et al. Risk of venous thromboembolism in women with polycystic ovary syndrome: a population-based matched cohort analysis. CMAJ. Dec 3, 2012. [Epub ahead of print.]
2. Okoroh EM, Hooper WC, Atrash HK, et al. Is polycystic ovary syndrome another risk factor for venous thromboembolism? United States, 2003-2008. Am J Obstet Gynecol. 2012;207:377.e1-8. doi: 10.1016/j.ajog.2012.08.007. Epub 2012 Aug 10.