Residency · Residency · Obstetrics Gynecology
Venous Thromboembolism in Obstetrics and Gynecology
Introduction
Venous thromboembolism (VTE), encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE), is a leading cause of maternal mortality in developed countries and a significant complication of gynecologic surgery. Pregnancy confers a 4- to 5-fold increased VTE risk due to physiologic hypercoagulability, venous stasis, and vascular injury. Risk-stratified prevention, prompt diagnosis, and evidence-based treatment are essential competencies.
Pathophysiology
Virchow's triad -- hypercoagulability, venous stasis, and endothelial injury -- provides the conceptual framework. Pregnancy increases factors VII, VIII, X, von Willebrand factor, and fibrinogen while decreasing protein S and increasing resistance to activated protein C. Venous stasis results from uterine compression of the IVC and iliac veins plus progesterone-mediated venodilation. Left leg DVT predominates (approximately 80%) because the right iliac artery compresses the left iliac vein. The postpartum period carries the highest daily risk, peaking in the first 1-2 weeks.
Risk Factors
Obstetric risk factors include cesarean delivery (especially emergency, increasing risk 2-5 fold), preeclampsia, postpartum hemorrhage, transfusion, immobilization, obesity (BMI greater than 30 doubles risk; greater than 40 confers 5-fold increase), and ART. Key thrombophilias include Factor V Leiden (7-8 fold increase), prothrombin gene mutation (3-4 fold), antithrombin deficiency (30-50% risk without prophylaxis), and antiphospholipid syndrome. For gynecologic surgery, malignancy is the strongest risk factor, with the Caprini model providing standardized stratification.
<image>Flowchart illustrating VTE risk stratification in pregnancy using maternal risk factors, thrombophilia status, and prior VTE history, with corresponding prophylaxis recommendations ranging from surveillance alone to therapeutic anticoagulation</image>
Diagnosis
Deep Vein Thrombosis
Compression ultrasonography is the first-line test with sensitivity and specificity exceeding 95% for proximal DVT. D-dimer is physiologically elevated in pregnancy and cannot be used to exclude VTE. MR venography may be considered for suspected iliac vein thrombosis when ultrasound is non-diagnostic.
Pulmonary Embolism
The diagnostic approach begins with CXR and ECG. If CXR is normal, V/Q scan is preferred (lower breast radiation dose). If CXR is abnormal or V/Q indeterminate, CT pulmonary angiography is appropriate. Neither modality exceeds the 50 mGy threshold for fetal harm. Echocardiography identifies right ventricular strain in massive PE.
Treatment
Anticoagulation in Pregnancy
LMWH (enoxaparin 1 mg/kg every 12 hours) is the treatment of choice. UFH is preferred when rapid reversal may be needed. Warfarin is contraindicated in pregnancy (teratogenic) but safe postpartum and compatible with breastfeeding. DOACs are contraindicated in pregnancy. Anticoagulation continues throughout pregnancy and for at least 6 weeks postpartum, with minimum total duration of 3 months.
Peripartum Management
LMWH is discontinued 24 hours before planned delivery (12 hours for prophylactic dosing). Neuraxial anesthesia requires at least 12 hours after prophylactic and 24 hours after therapeutic LMWH. Postpartum restart is 4-6 hours after vaginal and 6-12 hours after cesarean delivery. Warfarin transition targets INR 2.0-3.0 with LMWH overlap for at least 5 days.
Massive PE
Systemic thrombolysis (alteplase 100 mg IV over 2 hours) is warranted for hemodynamic instability despite bleeding risks -- pregnancy is a relative, not absolute, contraindication. Surgical embolectomy and catheter-directed therapy are alternatives. IVC filters are reserved for patients with absolute contraindications to anticoagulation.
<image>Diagnostic algorithm for suspected pulmonary embolism in pregnancy, showing initial chest X-ray and ECG, followed by V/Q scan or CT pulmonary angiography based on CXR findings, with decision points for treatment initiation</image>
Prophylaxis
Obstetric VTE Prophylaxis
Risk assessment occurs at first prenatal visit, upon admission, and postpartum. Antepartum prophylaxis is indicated for prior VTE, high-risk thrombophilia, or antiphospholipid syndrome. Post-cesarean pharmacologic prophylaxis is recommended with additional risk factors. Mechanical prophylaxis (SCDs) is used during and after cesarean for all patients.
Gynecologic Surgical VTE Prophylaxis
Low risk (Caprini 0-1) requires early ambulation only. Moderate risk (Caprini 2) warrants LMWH/UFH or mechanical prophylaxis. High risk (Caprini 3-4) requires pharmacologic plus mechanical prophylaxis. Highest risk (Caprini 5 or greater, gynecologic oncology) adds extended 28-day prophylaxis.
| Caprini Score | Risk Level | Prophylaxis |
|---|---|---|
| 0-1 | Low | Early ambulation only |
| 2 | Moderate | LMWH/UFH or mechanical (SCDs) |
| 3-4 | High | Pharmacologic + mechanical |
| ≥5 (gyn oncology) | Highest | Pharmacologic + mechanical + extended 28-day prophylaxis |
<image>Infographic showing Caprini Risk Assessment Model categories with corresponding VTE prophylaxis recommendations for gynecologic surgery patients, from early ambulation to extended pharmacologic prophylaxis</image>
Clinical Pearls
D-dimer cannot be used to exclude VTE in pregnancy -- proceed directly to imaging when clinical suspicion exists. LMWH is the cornerstone of VTE treatment in pregnancy; warfarin and DOACs are contraindicated during gestation. Left leg DVT predominates due to right iliac artery compression of the left iliac vein. Extended 28-day postoperative thromboprophylaxis reduces VTE by 50% in gynecologic oncology patients. Massive PE with hemodynamic instability warrants systemic thrombolysis even in pregnancy -- maternal survival takes priority.
References
- Bates SM, Rajasekhar A, Engeling S, et al. American Society of Hematology 2018 guidelines for management of venous thromboembolism: venous thromboembolism in the context of pregnancy. Blood Adv. 2018;2(22):3317-3359.
- Royal College of Obstetricians and Gynaecologists. Reducing the risk of venous thromboembolism during pregnancy and the puerperium. Green-top Guideline No. 37a. RCOG; 2015.
- American College of Obstetricians and Gynecologists. Thromboembolism in pregnancy. Practice Bulletin No. 196. Obstet Gynecol. 2018;132(1):e1-e17.
- Gould MK, Garcia DA, Wren SM, et al. Prevention of VTE in nonorthopedic surgical patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: ACCP Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e227S-e277S.
