What causes postpartum leg swelling?

Postpartum Leg Swelling: Causes and Management

Primary Causes

Postpartum leg swelling is most commonly caused by physiologic fluid redistribution and edema, but deep vein thrombosis (DVT) must be urgently excluded, particularly when swelling is unilateral, painful, or associated with other concerning features. 1

Physiologic Postpartum Edema

• Normal fluid shifts occur after delivery as pregnancy-related plasma volume expansion resolves and interstitial fluid mobilizes back into the vascular space 2
• Bilateral leg swelling without pain, redness, or warmth typically represents benign postpartum edema 1
• This physiologic edema peaks around postpartum days 3-5 and gradually resolves over 1-2 weeks 1

Deep Vein Thrombosis (DVT)

• The postpartum period carries the highest daily risk for pregnancy-associated VTE, with an estimated incidence of 1-2 per 1,000 deliveries 2
• Risk is particularly elevated after cesarean delivery compared to vaginal delivery 2
• DVT accounts for the majority of postpartum VTE events, with 85% occurring on the left side due to compression of the left iliac vein by the right iliac artery 1
• The postpartum period represents the most critical time, as the majority of hypertension-related maternal deaths and VTE-related deaths occur after delivery 2, 3

Clinical Red Flags Requiring Urgent DVT Evaluation

Any of the following features mandate immediate compression ultrasound to rule out DVT: 1

• Unilateral leg swelling (particularly left-sided) 1
• Calf circumference difference ≥2 cm between legs 1
• Associated pain, redness, or warmth 1
• Pain in the buttock, groin, flank, or abdomen (suggests isolated iliac vein thrombosis) 1
• Recent cesarean delivery (major risk factor) 2

Risk Factors for Postpartum DVT

Major Risk Factors (requiring prophylaxis with single factor present):

• Previous personal history of DVT or pulmonary embolism 2
• Known inherited thrombophilia (high-risk or low-risk) 2
• Cesarean delivery, especially emergency cesarean 2

Minor Risk Factors (requiring prophylaxis with ≥2 factors present):

• BMI >30 kg/m² 2
• Multiple pregnancy 2
• Postpartum hemorrhage >1 L 2
• Smoking >10 cigarettes/day 2
• Presence of indwelling venous catheters or devices 2

Diagnostic Algorithm

Step 1: Immediate Assessment

• Perform compression ultrasound of the proximal leg veins immediately if any red flags are present 1, 4
• Focus on the common femoral and popliteal veins initially 4
• Position the patient with lower extremities dependent to facilitate vein distension 4

Step 2: If Initial Ultrasound is Positive

• Initiate therapeutic-dose low molecular weight heparin (LMWH) immediately without waiting for confirmatory testing 1, 4
• Weight-adjusted dosing, twice daily 1
• Continue for minimum 3 months or at least 6 weeks postpartum 1

Step 3: If Initial Ultrasound is Negative but Suspicion Remains High

• Perform serial compression ultrasound on day 3 and day 7 1
• D-dimer testing can be considered, though levels are physiologically elevated postpartum and should not be relied upon solely 1
• Consider imaging of iliac veins if extensive unexplained leg swelling persists with negative proximal ultrasound 4

Management of Confirmed DVT

The European Society of Cardiology recommends therapeutic-dose LMWH as first-line treatment: 1

• Low molecular weight heparin is the preferred thromboprophylactic agent in pregnancy and postpartum 2
• Initiate immediately upon diagnosis 1
• Weight-adjusted dosing, administered subcutaneously twice daily 1
• Continue for minimum 3 months total or at least 6 weeks postpartum, whichever is longer 1
• Vitamin K antagonists (warfarin) may be started on postpartum day 2 if no significant bleeding occurred, with target INR 2-3 1
• Do not use rivaroxaban or other direct oral anticoagulants in breastfeeding women without clear safety data 1

Management of Physiologic Postpartum Edema

For bilateral leg swelling without concerning features, conservative management is appropriate: 1

• Graduated compression stockings (compression class 1, occasionally class 2) for all women with postpartum leg edema 1
• Leg elevation when resting 1
• Early mobilization and regular physical activity 1
• Sequential compression devices if patient had cesarean delivery, used continuously until fully ambulatory 2

Critical Pitfalls to Avoid

• Never dismiss unilateral leg swelling as "normal postpartum edema" without ruling out DVT, as pulmonary embolism can be fatal 1
• Do not rely solely on D-dimer in the postpartum period, as levels remain physiologically elevated 1
• Do not delay serial ultrasound if initial imaging is negative but clinical suspicion remains high 1
• A negative lower extremity ultrasound does not rule out pulmonary embolism 4
• Patients with suspected isolated calf DVT require repeat venous evaluation if not treated with anticoagulation 4

Institutional Protocols

Each institution should develop a patient safety bundle with an institutional protocol for VTE prophylaxis among women who undergo cesarean delivery (Best Practice recommendation) 2