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GP Evidence Summary
Hormone therapy does not increase risk of recurrent venous thromboembolism in women who are on full-dose anticoagulation
Question
In women with venous thromboembolism (VTE) on full-dose anticoagulation, does hormone therapy increase the risk of recurrent VTE compared with no hormone therapy?
The study
Who? The study included 1888 women who were treated for acute symptomatic deep vein thrombosis or pulmonary embolism with enoxaparin plus a vitamin K antagonist or rivaroxaban as part of the EINSTEIN DVT/PE randomized clinical trials.
What? The study compared the risk of recurrent VTE in women on full-dose anticoagulation who were taking hormone therapy versus those who were not taking hormone therapy.
| Hormone therapy* | vs | No hormone therapy* |
|---|---|---|
| Hormone therapy included estrogen-only pills, combined estrogen–progesterone contraceptives, and progestin-only contraceptives (including pills, implants, injectables, and intrauterine devices). | No hormone therapy. |
*All women were on full-dose anticoagulation with enoxaparin plus a vitamin K antagonist or rivaroxaban.
What the researchers found
The rate of recurrent VTE did not differ in women who continued or started hormone therapy compared with women who were not on hormone therapy.
The bottom line
In women who are fully anticoagulated for VTE, hormone therapy did not increase risk of recurrent VTE.
Summary of findings
Hormone therapy vs no hormone therapy in women who are on full-dose anticoagulants for VTE
| Outcomes at 3 to 12 months | Rate of events with hormone therapy | Rate of events with no hormone therapy | Absolute effect of hormone therapy |
|---|---|---|---|
| Recurrent VTE | 4 out of 100 women per year | 5 out of 100 women per year | No effect* |
*Although the rates for the 2 groups look different, the differences were not statistically significant—this means that the difference could simply be due to chance rather than due to the different treatments.
This Evidence Summary is based on the following study:
Martinelli I, Lensing AW, Middeldorp S, et al. Recurrent venous thromboembolism and abnormal uterine bleeding with anticoagulant and hormone therapy use. Blood. 2016 Mar 17;127(11):1417-25. PubMed
No need to stop hormone therapy in women who are taking full-dose anticoagulation
Hormone therapy, in the form of oral contraceptive therapy or as replacement therapy for menopause, increases the risk of venous thrombosis. For this reason, it is common for women with VTE to be told they must immediately stop hormone therapy. Although well-intended, there are several potential negative consequences to this advice:
- increased risk of fetal anomalies if a woman becomes pregnant while on anticoagulant therapy;
- increased risk of an unwanted pregnancy (other methods of contraception can be more burdensome and less reliable); and
- increased risk of menorrhagia in women who were taking hormone therapy to control this problem.
These risks might be worth accepting if we knew that continuing hormone therapy was harmful in women with VTE. However, the post hoc analysis of VTE treatment studies summarized above provides reassurance that continuing hormone therapy does not increase the risk of recurrent VTE. Instead, anticoagulant therapy likely suppresses the prothrombotic effect of hormones.
Doctor, do I have to stop taking my birth control pills because I have a blood clot?
No, not if you are on blood thinners and are taking them properly. However, when it is time for you to stop blood thinners, we will need to talk again about the risks versus benefits of hormone therapy because you will no longer have the protection of blood thinners.
Jameel Abdulrehman, MD, FRCPC
Dr. Abdulrehman completed his Internal Medicine residency at Western University and his Adult Hematology residency at the University of Alberta. He is currently pursuing a clinical fellowship in Thrombosis and Hemostasis at the University of Toronto.
Dr. Abdulrehman's CanVECTOR project aims to investigate the use of DOACs in obese patients.
Lori-Ann Linkins, MD, MSc (Clin Epi), FRCPC
Dr. Linkins is an Associate Professor of Medicine (thrombosis) at McMaster University in Hamilton, Canada. She holds a Masters Degree in Health Research Methodology and is a Deputy Editor with the Health Information Research Unit, McMaster. Her research interests include heparin-induced thrombocytopenia and cancer-associated thrombosis. She was editor of the ACCP Guidelines, 9th Edition HIT chapter and is currently a member of the ASH VTE Guidelines HIT Panel.
Published: Tuesday, April 18, 2017
Please note that the information contained herein is not to be interpreted as an alternative to medical advice from a professional healthcare provider. If you have any questions about any medical matter, you should consult your professional healthcare providers, and should never delay seeking medical advice, disregard medical advice or discontinue medication based on information provided here.
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, McMaster University