Postpartum Deep Vein Thrombosis

Postpartum deep vein thrombosis is a blood clot in the deep veins of the leg or pelvis in the 6 weeks after birth, the highest risk period being the first 2 weeks. The risk is many times that of a nonpregnant woman, and clots are more often in the left leg and iliac veins. It matters because the clot can travel to the lungs and cause death, and delayed treatment leaves chronic leg swelling.

• Risk factors: caesarean section, postpartum haemorrhage, preeclampsia, infection, immobility, body mass index above 30 kg/m2, age above 35 years, previous clot, thrombophilia, sickle cell disease, smoking.
• Most clots are proximal (iliofemoral), which carry the highest risk of embolism.
• Prophylaxis in high-risk women reduces the risk.

Women have unilateral leg pain, swelling, warmth and tenderness, and sometimes low grade fever. Iliac vein clots cause swelling of the whole leg, buttock or groin pain and lower abdominal pain.

• Calf circumference more than 2 cm larger than the other leg, measured 10 cm below the tibial tuberosity.
• Pitting oedema and distended superficial veins; leg may be pale or blue.
• Differential diagnosis: cellulitis, muscle strain or tear, ruptured Baker cyst, superficial thrombophlebitis, lymphoedema, pelvic haematoma, septic pelvic thrombophlebitis, hip or sciatic pain, venous insufficiency.
• Complications: pulmonary embolism, post-thrombotic syndrome, recurrent clot, venous ulcers, bleeding on anticoagulation, heparin-induced thrombocytopenia, maternal death.

The approach is clinical probability followed by compression ultrasound.

• Compression duplex ultrasound of the leg veins; repeat at 3 to 7 days if negative and suspicion remains; ultrasound of the iliac veins or MRI venography if the whole leg is swollen with a negative femoral scan.
• D-dimer is raised after birth and is not reliable.
• Full blood count and platelets, creatinine, liver enzymes, prothrombin time and activated partial thromboplastin time before anticoagulation.
• Thrombophilia tests (antiphospholipid antibodies, antithrombin, protein C and S) after 3 months, away from acute clot and anticoagulants.

The principle is immediate full dose anticoagulation, continued for at least 3 months and not less than 6 weeks after birth.

• Supportive: leg elevation; early walking once anticoagulated and pain allows; graduated compression stockings of 20 to 30 mmHg for symptom relief; fluids; stop smoking; breastfeeding continues.
• Pharmacological: enoxaparin 1 mg/kg subcutaneous 12-hourly (or 1.5 mg/kg once daily) for at least 3 months; unfractionated heparin 80 units/kg IV bolus then 18 units/kg/hour adjusted to an activated partial thromboplastin time of 1.5 to 2.5 times control for creatinine clearance below 30 mL/minute, massive iliofemoral clot or when thrombolysis may be needed; warfarin 5 mg oral once daily started with enoxaparin, the enoxaparin continuing for at least 5 days until the INR is 2.0 to 3.0 on 2 readings 24 hours apart, then warfarin alone to complete 3 months; paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours); avoid NSAIDs while anticoagulated; direct oral anticoagulants are not used in breastfeeding.
• Procedures: inferior vena cava filter if anticoagulation is contraindicated or clot recurs despite full treatment; catheter directed thrombolysis or thrombectomy for limb threatening iliofemoral thrombosis (phlegmasia).
• Special groups: renal impairment (creatinine clearance below 30 mL/minute) uses unfractionated heparin or enoxaparin 1 mg/kg once daily with anti-Xa monitoring; antiphospholipid syndrome uses warfarin with INR 2.0 to 3.0 long term or full dose enoxaparin; platelets falling by 50 percent after day 5 of heparin suggest heparin-induced thrombocytopenia and need specialist anticoagulation; obese women above 100 kg have enoxaparin by weight with anti-Xa monitoring; warfarin and heparin are compatible with breastfeeding.
• Red flags: breathlessness, chest pain, haemoptysis, syncope, blue or white swollen leg, bleeding, severe headache, platelets falling.
• Follow-up: platelets on days 7 and 14 of heparin; INR twice weekly until stable then weekly; review at 6 weeks and 3 months; plan prophylaxis with enoxaparin 40 mg subcutaneous once daily in any later pregnancy and for 6 weeks after birth.