Contraception and Venous Thromboembolism

Oestrogen in combined methods increases venous thromboembolism risk; progestin-only methods increase it little or not at all, with DMPA the possible exception. A patient with past or current thrombosis, or an inherited thrombophilia, still needs reliable contraception, especially when on anticoagulants (warfarin is teratogenic) or after a pregnancy that raises recurrence risk.

Assessment. Type, site and date of thrombosis; provoked or unprovoked; current anticoagulant and its duration; family history; known thrombophilia (factor V Leiden, prothrombin mutation, protein C or S or antithrombin deficiency, antiphospholipid antibodies); cancer, immobility, surgery, obesity, pregnancy and smoking status.

Anticoagulation and bleeding. Women on anticoagulants often have heavy menstrual bleeding, and the levonorgestrel 52 mg device is useful in controlling it.

Antiphospholipid syndrome. Positive or unknown antiphospholipid antibodies in lupus carry category 4 for combined pills and category 3 for progestin-only pills, injectables, implants and the levonorgestrel device; the copper device is category 1.

Effectiveness. As for the method in question.

Eligibility.

Method comparison. The copper intrauterine device is category 1 in all situations and is the safest choice. The levonorgestrel 52 mg device, implants and progestin-only pills are acceptable after thrombosis. DMPA is used with more caution because some data link it with higher thrombotic risk.

Interaction with warfarin. Hormonal methods do not reduce warfarin effect meaningfully, but warfarin is teratogenic in pregnancy so contraception is essential.

Special groups. Postpartum women with other risk factors have raised risk through 6 weeks; avoid combined methods. Pregnancy loss and abortion do not change eligibility.

Regimen lines.

• Copper T 380A: up to 12 years; levonorgestrel 52 mg device: 5 years; insertion within 12 days of the start of bleeding or at any time if reasonably not pregnant; no backup.

• Etonogestrel 68 mg rod: 3 years; levonorgestrel two 75 mg rods: 5 years or 3 years by system; backup 7 days if inserted after day 7 of bleeding.

• Progestin-only pill: one tablet daily without a break; late window by type; backup 2 days after a late or missed pill.

• DMPA 150 mg intramuscularly or 104 mg subcutaneously every 13 weeks, up to 4 weeks late: use only with informed consent if other methods are unsuitable.

• Combined methods: not used after thrombosis or with a thrombogenic mutation.

Emergency contraception. Levonorgestrel 1.5 mg within 120 hours; the copper device within 5 days; both are safe after thrombosis because they involve no sustained oestrogen exposure.

Starting during treatment. Contraception can begin while the patient is anticoagulated; no wait is needed for implant or device insertion, although bleeding or haematoma at the site is more likely.

Follow up. Review symptoms of recurrence and bleeding at each visit; review when anticoagulation stops or changes.

Suspected recurrence on any method. Unilateral leg pain or swelling, chest pain, breathlessness or haemoptysis needs same-day assessment and imaging; stop any combined method.

Heavy bleeding on anticoagulation. Levonorgestrel 52 mg device preferred; tranexamic acid is not used because of thrombosis risk; ibuprofen is avoided with anticoagulants; correct anaemia and review the anticoagulant dose.

Pregnancy on warfarin. Urgent specialist review for change to low molecular weight heparin before 6 weeks.

Hormonal method started before thrombophilia was known. Stop an oestrogen-containing method when the diagnosis is made and offer a copper or levonorgestrel device or a progestin-only method.

Red flags. Leg swelling, chest pain, haemoptysis, severe headache, heavy bleeding.

Referral and escalation. Refer suspected pulmonary embolism, recurrent thrombosis, unprovoked thrombosis in young patients, thrombophilia for counselling, and pregnancy on anticoagulation.