What does ACOG recommend for venous thromboembolism risk assessment and pharmacologic and mechanical prophylaxis in pregnant women, both ante‑partum and post‑partum (including after cesarean delivery)?

ACOG VTE Prophylaxis Guidelines for Pregnancy

Universal Mechanical Prophylaxis for All Cesarean Deliveries

All women undergoing cesarean delivery must receive sequential compression devices (SCDs) starting before surgery and continuing until fully ambulatory, regardless of other risk factors (GRADE 1C). 1

• This is a universal recommendation endorsed by both ACOG and the Society for Maternal-Fetal Medicine (SMFM). 1
• SCDs should be applied preoperatively and maintained continuously throughout the hospitalization until the patient achieves complete ambulation. 1, 2

Risk Stratification Framework

ACOG recommends screening all pregnant women for VTE risk factors, using a tiered approach based on major and minor risk factors. 1

Major Risk Factors (any one triggers pharmacologic prophylaxis):

• Prior personal history of DVT or pulmonary embolism 1, 2
• Inherited thrombophilia (high-risk: antithrombin deficiency, homozygous Factor V Leiden or prothrombin G20210A, compound heterozygous) 1, 2
• Antepartum immobility ≥1 week 2
• Preeclampsia with fetal growth restriction 2
• Antiphospholipid antibody syndrome 1

Minor Risk Factors (two or more trigger pharmacologic prophylaxis):

• Advanced maternal age (≥35 years) 2
• Obesity (BMI ≥30) 2, 3
• Current smoking 2
• Family history of VTE 2
• Varicose veins 2

The ACCP suggests that when absolute VTE risk exceeds 3%, pharmacologic prophylaxis benefits outweigh harms—this threshold is reached with one major risk factor OR two or more minor risk factors. 1, 2

Pharmacologic Prophylaxis Recommendations

Agent Selection

Low-molecular-weight heparin (enoxaparin) is the preferred thromboprophylactic agent in pregnancy and the postpartum period (GRADE 1C). 1, 2

Standard Dosing

• Enoxaparin 40 mg subcutaneously once daily for women with standard body habitus 2, 3
• Initiate postoperatively once hemostasis is assured 2

Obesity-Specific Dosing

For Class III obesity (BMI ≥40), intermediate-dose enoxaparin 40 mg subcutaneously every 12 hours is recommended rather than standard once-daily dosing (GRADE 2C). 1, 2

• Standard prophylactic dosing (40 mg once daily) results in subtherapeutic anti-Xa levels in the majority of patients with BMI ≥40. 2
• Intermediate-dose enoxaparin should not be initiated until at least 24 hours after neuraxial anesthesia (minimum 4 hours after epidural catheter removal). 2

Renal Impairment Considerations

• If creatinine clearance <30 mL/min, use unfractionated heparin (5,000-10,000 units subcutaneously every 8-12 hours) instead of enoxaparin. 2

Duration of Prophylaxis

Mechanical Prophylaxis

• Continue SCDs until the patient is fully ambulatory. 1, 2

Pharmacologic Prophylaxis

• Minimum 10 days for intermediate-risk patients (one major or two minor risk factors). 2
• Extended to 6 weeks postpartum when risk factors persist (GRADE 2C). 1, 2

High-Risk Populations Requiring Extended Combined Prophylaxis

Women with prior VTE or inherited thrombophilia should receive both mechanical and pharmacologic prophylaxis for 6 weeks postpartum (GRADE 2C). 1

This applies to:

• Any woman with previous DVT or PE 1
• Women with inherited thrombophilia (high-risk or low-risk) regardless of prior VTE history 1
• Women with antiphospholipid antibody syndrome 1

Vaginal Delivery Considerations

For vaginal delivery, obesity alone does not mandate pharmacologic prophylaxis—early ambulation is sufficient. 3

• Pharmacologic prophylaxis after vaginal delivery is reserved for women with major risk factors or multiple minor risk factors beyond obesity alone. 3
• This contrasts sharply with cesarean delivery, where the surgical procedure itself elevates baseline VTE risk. 1, 3

Antepartum Prophylaxis

For pregnant women with prior VTE not on long-term anticoagulation:

• If prior VTE was associated with a transient risk factor no longer present: clinical surveillance antepartum plus postpartum prophylaxis (GRADE 1C). 4
• If prior VTE was unprovoked or associated with pregnancy/estrogen: prophylactic or intermediate-dose LMWH throughout pregnancy plus 6 weeks postpartum (GRADE 2C). 4

For women with thrombophilia but no prior VTE:

• Antithrombin deficiency: both antepartum and postpartum prophylaxis (GRADE 2C). 4
• Other high-risk thrombophilias: antepartum prophylactic or intermediate-dose LMWH plus postpartum prophylaxis (GRADE 2C). 4

Critical Timing Around Delivery

• Discontinue LMWH at least 24 hours before planned cesarean delivery or neuraxial anesthesia. 2
• Resume pharmacologic prophylaxis 6-12 hours after cesarean delivery if no increased bleeding risk. 5
• For vaginal delivery, resume 4-6 hours postpartum if hemostasis is adequate. 5

Common Pitfalls to Avoid

• Do not use standard-dose enoxaparin (40 mg once daily) in Class III obesity—this is inadequate and leaves patients under-protected. 2
• Do not use direct oral anticoagulants (DOACs) in the postpartum period—insufficient safety data exists for apixaban, rivaroxaban, or dabigatran during lactation. 2
• Do not rely on early mobilization alone when two or more minor risk factors are present—this is appropriate only for patients with no identified VTE risk factors. 2
• Do not initiate intermediate-dose enoxaparin before 24 hours post-neuraxial block—this significantly increases spinal hematoma risk. 2

Institutional Implementation

SMFM recommends that each institution develop a standardized patient safety bundle with a VTE prophylaxis protocol for cesarean delivery (Best Practice). 1, 2

• Protocols should integrate SCD application, risk stratification, LMWH dosing, and renal function screening. 2
• Standardized order sets reduce variation and improve compliance with evidence-based prophylaxis. 1