Pulmonary Embolism in Pregnancy

Pulmonary embolism in pregnancy is blockage of the pulmonary arteries by clot, usually from leg or pelvic veins. It is an important cause of direct maternal death, with the highest risk after caesarean section and in the weeks after delivery. It matters because symptoms overlap with normal pregnancy, and untreated massive embolism is fatal.

• Risk factors: previous thrombosis, thrombophilia, obesity, caesarean section, immobility, preeclampsia, infection, age above 35 years.
• Many women with embolism have a detectable leg clot.
• Fetal radiation dose from diagnostic imaging is very low.

Women have sudden breathlessness, pleuritic chest pain, cough, haemoptysis, palpitations and sometimes collapse, with tachycardia, tachypnoea and low oxygen saturation. Massive embolism causes hypotension and shock.

• Respiratory rate above 20 per minute and pulse above 100 per minute.
• Raised jugular venous pressure and loud second heart sound in large emboli.
• Differential diagnosis: pneumonia, asthma, peripartum cardiomyopathy, amniotic fluid embolism, pneumothorax, aortic dissection, anxiety, normal pregnancy breathlessness.
• Complications: shock, cardiac arrest, right heart failure, chronic thromboembolic hypertension, recurrence, bleeding on anticoagulation, maternal death.

The approach is clinical suspicion with leg ultrasound and definitive lung imaging.

• Oxygen saturation, arterial blood gas, ECG (sinus tachycardia, S1Q3T3 pattern, right bundle branch block), chest X-ray with shielding.
• Compression ultrasound of the legs first; a clot confirms the need for treatment and avoids lung imaging.
• CT pulmonary angiography (fetal dose below 0.1 mGy), or ventilation perfusion scan when the chest X-ray is normal.
• Echocardiography for right ventricular strain; troponin and natriuretic peptide for severity; D-dimer is unreliable.

The principle is immediate anticoagulation with resuscitation, thrombolysis for shock, and anticoagulation continued to 6 weeks after delivery.

• Supportive: sit upright; oxygen 4 to 10 L/min to keep saturation at 95 percent or above; two IV cannulae; left lateral tilt; cautious fluid 250 to 500 mL; high dependency care; continuous fetal monitoring when viable.
• Pharmacological: unfractionated heparin 80 units/kg IV bolus then 18 units/kg/hour adjusted to an aPTT of 1.5 to 2.5 times control for massive or submassive embolism, or enoxaparin 1 mg/kg subcutaneous 12-hourly for stable women; alteplase 10 mg IV bolus over 2 minutes then 90 mg IV over 2 hours for shock (or streptokinase 250,000 units IV over 30 minutes then 100,000 units per hour for 24 hours); noradrenaline 0.05 to 0.5 micrograms/kg/minute IV for hypotension; morphine 2.5 mg IV for pain; warfarin 5 mg oral daily after delivery with enoxaparin overlap for 5 days until the INR is 2 to 3 for 24 hours; no direct oral anticoagulants.
• Procedures: catheter directed or surgical embolectomy for failed thrombolysis or contraindication; perimortem caesarean section within 5 minutes of arrest after 20 weeks; inferior vena cava filter if anticoagulation fails or is contraindicated; stop therapeutic heparin 24 hours before planned delivery.
• Special groups: renal impairment uses unfractionated heparin; suspected heparin induced thrombocytopenia needs specialist anticoagulation; after delivery breastfeeding is compatible with warfarin and enoxaparin.
• Red flags: systolic blood pressure below 90 mmHg, oxygen saturation below 90 percent, syncope, haemoptysis, bleeding, severe headache, fetal bradycardia.
• Follow-up: platelets at day 7 to 14 of heparin; review every 4 weeks; delivery plan with anaesthetist and obstetric physician; review at 6 weeks postpartum, with echocardiography if breathlessness persists.