Thromboembolism is a leading cause of maternal morbidity and mortality in the United States. The risk of venous thromboembolism (VTE) is increased four-fold during pregnancy and another five-fold for 6 weeks following delivery. The increased VTE risk for these women is mainly attributed to pregnancy because it puts the body in an increased thrombogenic state, but physiologic factors, such as an enlarged uterus and compressed blood vessels at the time of childbirth, also play a role. Other risk factors include having a prior VTE, family history of thrombosis, smoking, high blood pressure, obesity, and operative delivery. The consequences of VTE during pregnancy can be severe and often stem from a failure in diagnosis rather than inadequate therapy.

An updated practice bulletin from the American College of Obstetricians & Gynecologists (ACOG) was published in the September 2011 issue of Obstetrics & Gynecology to provide clinicians with updated information on the risk factors, diagnosis, management, and prevention of VTE. “This document places more emphasis on the acquired risk factors for VTE during pregnancy,” says Andra H. James, MD, who helped develop the bulletin. “The recommendations explain how to monitor women for thromboembolic events, address certain risk factors, and treat suspected or acute cases of VTE. The hope is that maternal deaths can be reduced if more clinicians adopt the recommendations provided in the bulletin.”

New Recommendations to Manage VTE

A major recommendation offered in the ACOG update is the use of compression ultrasonography of the proximal veins when signs or symptoms are suggestive of new onset DVT (Figure). Use of compression ultrasonography will indicate if treatment should be started or surveillance continued. “While warning signs in some may be evident early in pregnancy, others will develop symptoms that manifest later in pregnancy or after the baby is born,” Dr. James says. “Therefore, ongoing patient assessment is critical.”

The ACOG bulletin also includes more explicit recommendations for anticoagulant prevention of VTE in pregnancy (Table). Therapeutic anticoagulation is recommended for all women with acute VTE during pregnancy, most women with a history of thrombosis, and many of those at significant risk for VTE during pregnancy and postpartum (eg, women with high-risk acquired or inherited thrombophilias). “Due to a paucity of data on benefits versus risks among pregnant women, routine anticoagulation therapy is not warranted,” says Dr. James. Furthermore, the ACOG bulletin affirms that most women who take anticoagulation medications before pregnancy will need to continue to do so during pregnancy and postpartum. Another recommendation is that anticoagulant therapies be continued postpartum. This is because data show that clots can still occur during this period.

Cesarean Delivery & Thromboembolism

Cesarean delivery is an independent risk factor for thromboembolic events that nearly doubles a woman’s risk of VTE. An emphasis in the ACOG bulletin was placed on the increased risk of VTE due to obstetric complications and surgeries, including cesarean deliveries. Inflatable compression devices are recommended for use in women undergoing cesarean delivery, even if it’s a low-risk patient. “Fitting inflatable compression devices on legs before cesarean delivery appears to be a safe and potentially cost-effective preventive intervention,” says Dr. James. “Inflatable compression sleeves should be left in place until women are able to walk after delivery or until anticoagulation medication is resumed in women who had been on blood thinners during pregnancy.” ACOG notes, however, that an emergency cesarean delivery should not be delayed for the placement of compression devices.

Moving Forward with VTE Screening

While many clinicians have been accustomed to using the ACOG prenatal record—which routinely screens for VTE—it is critical that physicians continue to do the following as the adoption of electronic medical record systems increases:

Ask every woman if she has a history of thromboembolism.
Evaluate women who have a history of thromboembolism for the need for anticoagulants.
Evaluate and treat women with signs and symptoms of VTE during pregnancy.

“Assessment of signs and symptoms is essential because any delay in diagnosis and treatment can have devastating consequences,” says Dr. James. Future randomized clinical trials are needed to determine optimal regimens for preventing VTE in pregnancy and to assess if the use of anticoagulants can improve pregnancy outcomes. Research is also needed on preventive treatments for VTE during the postpartum period and on how to prevent arterial thromboembolism during and following pregnancy. “While thromboembolic events are not common, they can occur in healthy, young women,” Dr. James says. “These can be truly devastating, and we need more data on how to manage these cases.”


Practice bulletin no. 123: thromboembolism in pregnancy. Obstet Gynecol. 2011;118:718-729. Available at:

American College of Obstetricians and Gynecologists. Thromboembolism in Pregnancy. ACOG Practice Bulletin #19. August, 2000.

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