Contraception for a 22-Year-Old Woman on Warfarin
Progesterone-only contraception (option A) is the safest and most appropriate choice for this patient, as estrogen-containing methods are contraindicated in women on chronic anticoagulation due to increased thrombotic risk. 1, 2
Why Progesterone-Only Methods Are Preferred
Progestin-only contraceptives are generally considered safe in patients at high risk for thrombosis, including those on warfarin therapy. 2 The 2018 AHA/ACC guidelines explicitly classify estrogen-containing contraceptives as potentially harmful (Class III: Harm) for women at high risk of thromboembolic events, which includes those with mechanical valves requiring anticoagulation. 1
Specific Progesterone-Only Options
Long-acting reversible contraception (LARC) with the levonorgestrel IUD or etonogestrel implant represents the most effective progesterone-only choice, with failure rates of 0.2% and 0.05% respectively, compared to 9% for oral contraceptives. 3
The levonorgestrel-releasing IUD offers additional noncontraceptive benefits for women on anticoagulation, including treatment of menorrhagia that commonly occurs with warfarin therapy. 2, 4 Three observational studies demonstrated the LNG-IUD effectively treats menorrhagia in women on anticoagulation without major bleeding complications. 4
Depot medroxyprogesterone acetate (DMPA) is another option, though the ESC guidelines note potential for fluid retention must be considered. 1 One study showed DMPA prevented recurrent hemorrhagic ovarian cysts in women on chronic anticoagulation. 4
Why Other Options Are Inappropriate
Combined Oral Contraceptives (Option B) and Estrogen-Progesterone Patch (Option C)
Both combined hormonal methods are contraindicated because estrogen increases thrombotic risk. 1, 2 Combined estrogen-progestin contraceptives increase the risk of both venous and arterial thrombosis and are specifically contraindicated in women with a history of thrombosis or at high risk for thrombotic events. 2
Low-dose combined oral contraceptives containing ≤20 mcg ethinyl estradiol are only safe in women with low thrombogenic potential, explicitly excluding those with complex valvular disease or on anticoagulation. 1
The 2019 AHA/ACC guidelines state there are no data on whether warfarin adequately offsets the additional thrombotic risk from estrogen-containing contraception in high-risk patients. 1
Bilateral Tubal Ligation (Option D)
Tubal ligation is inappropriate as first-line contraception for a 22-year-old woman given her young age and the availability of highly effective, reversible alternatives. 1
While tubal ligation can be accomplished safely in most women, it carries recognized risks from anesthesia and abdominal insufflation. 1
Permanent sterilization should be reserved for women who have completed childbearing, not offered as primary contraception to a young woman with decades of reproductive potential remaining. 1
Clinical Implementation
No physical examination is required before initiating progesterone-only contraception, though pregnancy testing should be performed if the patient is sexually active. 3
One pharmacokinetic study found no statistically significant interaction between oral contraceptives and warfarin, suggesting hormonal contraception does not compromise anticoagulation efficacy. 4
The levonorgestrel IUD can be inserted at any time if reasonably certain the patient is not pregnant, with backup contraception (condoms) recommended for 7 days if not inserted during menses. 3
Critical Caveat
Regardless of the contraceptive method chosen, condoms must be used at every sexual encounter for STI prevention, as hormonal contraceptives provide no protection against sexually transmitted infections. 3