Oral Contraceptives and Venous Thromboembolism: New Publication Covers FAQs


Few young women develop venous thromboembolism, but 2 circumstances increase risk in women of childbearing age: pregnancy, and the use of sex hormones, including oral contraceptives.

Few young women develop venous thromboembolism (VTE). However, 2 circumstances increase risk in women of childbearing age: pregnancy, and the use of sex hormones, including oral contraceptives. Health agencies in numerous countries have made efforts to warn healthcare professionals about the increased risk related to these circumstances, but it appears that prescribing patterns are very difficult to change.

A team of researchers from Germany working in concert with King's College in London, UK, has published a paper, ahead-of-print in the journal Vasa, describing the use of various types of sex hormones, and its relationship to VTE. They review the most common relationships between sex hormones and VTE, risk factors, and counseling strategies.

The most important contributing factor is the individual patient’s baseline risk for VTE. Other factors include the hormones type and dose, the application route, and specific combinations of estrogen in the product used.

This review, which is comprehensive, addresses a number of questions that clinicians often ask. The researchers make a number of points with which pharmacists should be familiar:

  • Risk of VTE can increase by 2 to 4 times or more depending on the sex hormone used. They review available data for estrogens commonly used in today’s contraceptives, and hormone replacement therapy.
  • They indicate that patients who have had thromboembolic events in the past, have family histories of thromboembolic events, are older or heavier, smoke, or expect to be immobilized, or have histories of war family histories of thrombophilia are at highest risk. They recommend against routine thrombophilia screening.
  • Women who experience VTE reduce the risk of recurrent episodes by about 50% if they stop taking oral contraceptives.
  • It appears that women who develop VTE and are treated with anticoagulants may be able to take oral contraceptives. This is particularly important in women for whom unplanned pregnancy (which increases risk of VTE fivefold by itself) could be catastrophic. It is also important in women who are at elevated risk for menstrual bleeding complications. The researchers hasten to point out that the findings they describe apply only to the period of active treatment (3 to 6 months) with anticoagulants.
  • Current evidence seems to indicate that the transdermal route is much less likely to increase risk of venous thromboembolism than the oral route.


Sex hormones and venous thromboembolism—from contraception to hormone replacement therapy.Vasa. 2018 Jul 16:1-10. doi: 10.1024/0301-1526/a000726. [Epub ahead of print]

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