Safety of contraception among women using anticoagulant therapy: An updated systematic review

OBJECTIVE: Women on anticoagulant therapy are at risk for bleeding and may be at risk for recurrent thrombosis, which may be further increased with use of certain contraceptive methods. Our objective was to update a previous systematic review on safety of contraception among women on anticoagulant therapy. STUDY DESIGN: We searched multiple databases from inception through December 12, 2022 for articles on concurrent use of contraception and anticoagulant therapy. Outcomes were thromboembolism, bleeding, and drug-drug interactions. Among women on anticoagulant therapy, we compared outcomes for women using and not using contraception. We assessed risk of bias for each study, and certainty of evidence for all outcomes. RESULTS: Fourteen articles met inclusion criteria (12 were new); one had low risk of bias, three had moderate risk of bias, and 10 had high risk of bias. Anticoagulants examined included warfarin, heparin, aspirin, rivaroxaban, enoxaparin, phenindione, acenocoumarol, combined therapy, and unspecified. Four studies (two comparative and two non-comparative studies) in women using anticoagulant therapy found no evidence that use of combined or progestin-only hormonal contraceptive increased the risk of recurrent venous thromboembolism (VTE). Ten studies (four comparative and six non-comparative studies) examined uterine bleeding with use of anticoagulant therapy and generally found that bleeding was increased during use of copper intrauterine devices (IUDs) and decreased during use of levonorgestrel (LNG) IUDs. Two studies examined pharmacokinetic outcomes and found no decreases in anticoagulant levels with combined oral contraceptive exposure. CONCLUSIONS: Limited evidence suggests risk for recurrent VTE may not be increased with hormonal contraceptive use among women using anticoagulants. Bleeding among women on anticoagulant therapy might worsen with copper IUD use but might improve with LNG-IUD use. The certainty of evidence for most outcomes is very low. IMPLICATIONS: Women on anticoagulant therapy are at risk for recurrent thrombosis and bleeding, which might be further exacerbated with use of certain contraceptive methods. Additional evidence is needed on safety of concurrent use of anticoagulant medications and contraceptives.

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