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Risk of thromboembolism associated with non-oral contraceptives

Jennifer Bunn
in Women's/Men's Health
Photo: Shutterstock

Most women have known for years that oral birth control pills carry a small risk of blood clots (thromboembolism). There are now many alternatives to oral contraceptives, including skin patches and vaginal rings. There have been few studies regarding the risk of thromboembolism in women using these newer forms of birth control.

A study published recently on the BMJ (British Medical Journal) website included all Danish women who were not pregnant between the years 2001 and 2010, aged 15 to 49 years. None of the women had ever had a blood clot prior to the study. The study results are based on 9,429, 128 observation years. There were 3, 434 confirmed diagnoses of thromboembolism (first occurrence) during the study period. The study found:

  • the risk of a blood clot in women who did not use any form of birth control was an average of 2 events/10,000 exposure years
  • the risk of blood clot in women using a combined birth control pill containing levonorgesterol experienced 6.2 events/10,000 exposure years
  • the risk of blood clot in women using a skin patch for birth control was 9.7 events/10,000 exposure years
  • the risk of blood clot in women using a vaginal ring was 7.8 events/10,000 event years

The researchers calculated that if 2000 women using a vaginal ring and 1250 women using a skin patch switched to a combination birth control pill containing levonorgestrel, there would be one less occurrence of blood clot in a single year.

What is thromboembolism?

Venous thromboembolism is a condition that includes both DVT, or deep vein thrombosis, and pulmonary embolism. It can be fatal and is often under diagnosed, leading to complications and/or death.

Who is at risk?

Thromboembolism may be hereditary or acquired.
Hereditary causes include hypercoagulable states and thrombophilia:

  • Protein S or C deficiency
  • Increased levels of Factor Vlll
  • Deficiency of antithrombin
  • Gene mutation affecting prothrombin
  • Factor V Leiden mutation
  • Dysfibrinogenemia

Acquired causes include:

  • Body mass index greater than 30
  • Surgery/trauma
  • Certain medical illnesses (COPD, heart failure)
  • Immobilisation
  • Indwelling CVCs (central venous catheters), pacemakers
  • IBD (inflammatory bowel disease)
  • Air travel (due to immobility)
  • Previous thromboembolism
  • Myeloproliferative disorders
  • Some cancers and their treatments
  • HRT (hormone replacement therapy), birth control, pregnancy
  • Antiphospholipid syndrome
  • Heparin-induced thrombocytopenia

Signs/symptoms of thromboembolism

Symptoms of DVT include swelling and tenderness, most often in the lower leg. There may be increased warmth and erythema, as well as dilated veins (collateral circulation) on the leg. If the clot totally occludes venous outflow, ischemia and gangrene may result.

Pleuritic chest pain, tachypnea and dyspnea are commonly present in patients who have a pulmonary embolism. The client may have a fast heart rate and a cough that is tinged with blood. Cough is frequently present. The patient appears restless and apprehensive. Fever and rales may also be appreciated. Signs and symptoms of DVT may be found, or may not be seen unless an active search for DVT is undertaken.

Diagnosis of thromboembolism

Arterial blood gases, plasma D-dimer, chest x-ray, Doppler (duplex) ultrasound, pulmonary angiography, ventilation-perfusion scanning, spiral CT scanning and other tests may be used to determine whether the patient has a DVT or pulmonary embolus (or both).

Treatment of thromboembolism

Anticoagulants are given to prevent further clots from being deposited. Heparin is often used; some patients may be safely treated with LMWH (low molecular weight heparin). To prevent reoccurrence, warfarin is often prescribed for several months (and sometimes years, depending on the person’s condition and risk factors).

Thrombolytic therapy, such as urokinase, streptokinase and rt-PA are used to treat pulmonary embolism. Thrombolytic therapy is used to dissolve recent clots. Some patients who cannot take anticoagulants may have a vena caval filter inserted to trap lethal emboli. Others may require a pulmonary embolectomy to extract the clot; however, the mortality rate is high and the procedure is reserved for massive pulmonary emboli.

Women who use birth control, whether in pill, patch or vaginal ring form, should be educated on the signs and symptoms of thromboembolism. Women on birth control should be encouraged to quit smoking, as smoking raises the risk of thromboembolism.

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