Deep Vein Thrombosis and Pulmonary Embolus in Pregnancy
Basics
Description
Both pregnancy in and the puerperium are described as risk factors for deep vein thrombosis (DVT) and pulmonary embolism (PE); collectively referred to as venous thromboembolic disease. Pregnancy-related blood clot typically occur in the venous system of the lower extremity or in the iliac veins.
Epidemiology
Incidence
- Of venous thromboembolism (VTE) cases: DVT, 80%; PE, 20% (1)
- 1.4 in 1,000 pregnancies, including 1.1 DVT and 0.3 PE in 1,000
- Risk of VTE events is similar in all trimesters.
- Half of all cases occur within the 6-week postpartum period, and thus the risk per day is highest in the weeks following an obstetrical delivery (2).
- In pregnancy, DVT more likely in the left iliofemoral veins as iliac artery (40% increased cardiac output in pregnancy) compresses underlying iliac vein in the vessel’s pelvic course
- Leading cause of maternal death in developed countries—1.1 deaths per 100,000 deliveries
ALERT
5 times greater risk than in nonpregnant population (1)
5 times greater risk than in nonpregnant population (1)
Etiology and Pathophysiology
Virchow triad (1)
- Vascular injury: iliac vein injury during delivery
- Venous stasis: progesterone-induced venous dilatation, compression on inferior vena cava (IVC) and iliac veins by gravid uterus
- Hypercoagulability: ↑ coagulation factors (fibrin, factors II/VII/VIII/XI/X, von Willebrand factor [vWF]), ↓ fibrinolytic activity, and free protein S
Risk Factors
- History of VTE (15–25% are recurrent cases)
- Inherited or acquired thrombophilias
- High risk: homozygous factor V Leiden (RR:34), homozygous prothrombin G20210A mutation (RR:26), the previous two combined mutation (RR:44) (1)
- Low risk: heterozygous factor V Leiden (RR:8), heterozygous prothrombin G20210A (RR:7), antithrombin III (RR:5) deficiency, protein C (RR:5) or S (RR:3) deficiency. The relative risk is compared to all pregnancies (1); antiphospholipid syndrome (RR is uncertain) (3)
- Age >35 years old
- Obesity (BMI >30), smoking, parity ≥3
- Medical comorbidities: heart and lung disease, SLE, sickle cell, IBD, nephrotic syndrome, T1DM
- Obstetric risk factors include twin (and other multiple gestation), preeclampsia, cesarean section, prolonged labor (>24 hours), operative delivery, severe postpartum hemorrhage.
- Transient and potentially recurring risk factors include assisted reproductive technology (ART), in vitro fertilization (IVF), ovarian hyperstimulation syndrome (OHSS), any surgery during pregnancy, hyperemesis, dehydration, bed rest >3 days, systemic infection, long-distance travel (>4 hours).
ALERT
Risk of VTE is higher in the postpartum period; interestingly, 2/3 of DVTs happen antepartum and 60% of PEs postpartum. Postpartum incidence of VTE is 10 to 20 times higher than in the nonpregnant state and is especially high after cesarean.
Risk of VTE is higher in the postpartum period; interestingly, 2/3 of DVTs happen antepartum and 60% of PEs postpartum. Postpartum incidence of VTE is 10 to 20 times higher than in the nonpregnant state and is especially high after cesarean.
General Prevention
- Screening for thrombophilias even after diagnosis of VTE during pregnancy is not recommended (3)[C].
- Early mobilization, graduated compression stockings for low-risk groups
- Antepartum thromboprophylaxis for high-risk thrombophilia with family history of VTE, ≥2 prior VTE (unprovoked, pregnancy, or estrogen related) (3). If no family history, suggest postpartum prophylaxis for 6 weeks only with prophylactic or intermediate dose low-molecular-weight heparin (LMWH) (3)[B].
- Anticoagulation may not be required if prior VTE was not pregnancy related and associated with a risk factor no longer present.
- Consider thromboprophylaxis for past single episode of idiopathic VTE, low-risk thrombophilia with past VTE, morbid obesity (BMI >40), bedridden patients, and assisted reproduction technologies (3)[C].
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Citation
Domino, Frank J., et al., editors. "Deep Vein Thrombosis and Pulmonary Embolus in Pregnancy." 5-Minute Clinical Consult, 33rd ed., Wolters Kluwer, 2025. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688460/all/Deep_Vein_Thrombosis_and_Pulmonary_Embolus_in_Pregnancy.
Deep Vein Thrombosis and Pulmonary Embolus in Pregnancy. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2025. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688460/all/Deep_Vein_Thrombosis_and_Pulmonary_Embolus_in_Pregnancy. Accessed October 6, 2024.
Deep Vein Thrombosis and Pulmonary Embolus in Pregnancy. (2025). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (33rd ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688460/all/Deep_Vein_Thrombosis_and_Pulmonary_Embolus_in_Pregnancy
Deep Vein Thrombosis and Pulmonary Embolus in Pregnancy [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2025. [cited 2024 October 06]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688460/all/Deep_Vein_Thrombosis_and_Pulmonary_Embolus_in_Pregnancy.
* Article titles in AMA citation format should be in sentence-case
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ED - Baldor,Robert A,
ED - Golding,Jeremy,
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BT - 5-Minute Clinical Consult, Updating
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