The risk of recurrence in women with venous thromboembolism while using estrogens: a prospective cohort study

Summary Background The optimal duration of anticoagulation for women who had venous thromboembolism ( VTE ) associated with estrogen use is unknown. Objectives To test the hypothesis that women who had a first VTE while using estrogens have a low risk of recurrence. Methods A Prospective cohort study of 630 women (333 estrogen users, 297 non‐users) with a first VTE , who were followed for an average of 69 months after anticoagulation withdrawal. Women with a previous or secondary VTE , coagulation inhibitor deficiency, lupus anticoagulant, cancer, pregnancy, requirement of long‐term antithrombotic therapy or homozygosity or double heterozygosity for factor V Leiden and/or the G 20210 A prothrombin mutation were excluded. The endpoint was objectively documented symptomatic recurrent VTE . Results VTE recurred in 22 (7%) estrogen users and in 49 (17%) non‐users. After 1, 2 and 5 years, the cumulative probability of recurrence was 1% (95% confidence interval [ CI ], 0–2), 1% (95% CI , 0–2) and 6% (95% CI , 3–9) among estrogen users and 5% (95% CI , 2–7), 9% (95% CI , 6–13) and 17% (95% CI , 12–22) among non‐users. Compared with non‐users, estrogen users had an adjusted relative risk ( RR ) of recurrent VTE of 0.4 (95% CI , 0.2–0.8). Compared with non‐users in the respective age groups, the RR of recurrence was 0.4 (95% CI , 0.2–0.8) among estrogen‐containing‐contraceptive users and 0.7 (95% CI , 0.3–1.5) among women using estrogen‐containing menopausal hormone therapy. Conclusions Women who had their first VTE while using estrogens have a low risk of recurrent VTE . These women might not benefit from extended anticoagulant therapy.