Pregnancy in Women with a Prior Thrombosis (“Blood Clot”)

Posted On: November 14, 2017 By Nathan D. Fox, MD

When a patient experiences a blood clot in the leg (deep venous thrombosis) or of the lungs (pulmonary embolism), these can be life-threatening emergencies. Women with a history of a blood clot are at increased risk of recurrence during pregnancy.  However, that risk is influenced by the circumstances surrounding the original blood clot. For example, women with transient risk factors at the time of the blood clot (prolonged immobilization, major surgery, long flights) are less likely to have a recurrence in pregnancy compared to women whose clot occurred without provocation.  If the risk factor was estrogen-related (birth control pills, pregnancy), then the risk of recurrence would likely be high during a subsequent pregnancy.

Additionally, if a woman has an inherited or acquired thrombophilia (susceptibility to blood clotting), the likelihood of recurrence is high as well.

Due to this, a woman with a history of a blood clot should be seen in consultation prior to pregnancy to determine the exact circumstances surrounding her blood clot and possibly to test for certain types of thrombophilia.  Based on that information, a plan for pregnancy can be developed, as treatment is often required at the beginning of pregnancy.

Many women with a prior blood clot will require anticoagulation during pregnancy, which usually involves injections of blood thinners (unfractionated heparin or low molecular weight heparin) once or twice a day during pregnancy.  They are safe for the fetus.

It is important to note that the highest risk of a recurrent blood clot is actually after delivery, so the blood thinners need to be continued until several weeks postpartum.

Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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