Pulmonary Embolism in Pregnancy
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Direct answer
Pulmonary embolism remains a leading cause of maternal death in high-income settings, because pregnancy raises clotting factors and venous stasis. Suspicion rests on dyspnoea, pleuritic pain, tachycardia and signs of deep vein thrombosis, and imaging is chosen to limit fetal radiation. Therapeutic low molecular weight heparin is the mainstay, given throughout pregnancy and for at least six weeks after delivery, with warfarin and direct oral anticoagulants avoided.
What you must remember
- Presentation: sudden dyspnoea, pleuritic chest pain, tachycardia, haemoptysis and hypoxia, with leg swelling or calf tenderness suggesting DVT.
- Physiological D-dimer: D-dimer rises in normal pregnancy, so a raised result is not diagnostic and a negative result is less reliable for exclusion than it is outside pregnancy.
- Imaging choice: a chest radiograph first, then V/Q scan when the film is normal, with CTPA used when the radiograph is abnormal or V/Q is indeterminate.
- DVT: compression ultrasonography is the first test in symptomatic leg disease, and a positive result allows treatment without chest imaging.
- Treatment: weight-adjusted therapeutic low molecular weight heparin, with warfarin avoided in pregnancy and direct oral anticoagulants not used.
- Massive PE: thrombolysis is accepted in life-threatening instability despite fetal risk, with surgical embolectomy or extracorporeal support as alternatives in specialist centres.
- Duration: anticoagulation continues through pregnancy and for at least six weeks postpartum, with a total of at least three months.
A pathway from suspicion to delivery
A 31-year-old at 28 weeks presents with sudden breathlessness and a heart rate of 120. The risk to mother and fetus depends on acting quickly while choosing an imaging test that limits radiation, so the steps below run in parallel rather than one at a time.
- Assess the risk: estimate clinical probability (the Wells score is not validated in pregnancy), check for shock and hypoxia, and treat unstable patients without delay.
- Image safely: start with a chest radiograph, then V/Q scan when normal, and reserve CTPA for abnormal films or indeterminate V/Q.
- Start treatment: give therapeutic weight-adjusted low molecular weight heparin while awaiting results when suspicion is high.
- Treat severe PE: use thrombolysis for haemodynamic collapse, with ECMO or embolectomy in specialist centres.
- Plan delivery: stop low molecular weight heparin about 24 hours before induction or neuraxial block, and bridge with unfractionated heparin in high-risk women.
- Continue postpartum: keep anticoagulation for at least six weeks after delivery, to a total of at least three months.
Where the exam tries to catch you
PE questions often test the safe imaging choice and the correct anticoagulant, not the diagnosis itself.
- Trap: "Start warfarin because it is cheap and reliable." Correct: warfarin is teratogenic, so therapeutic low molecular weight heparin is used throughout pregnancy.
- Trap: "Use D-dimer to exclude PE in pregnancy." Correct: D-dimer rises physiologically, so imaging and clinical probability decide the diagnosis.
- Trap: "Avoid thrombolysis entirely in pregnancy." Correct: thrombolysis is accepted when the mother is in life-threatening haemodynamic collapse, despite the fetal risk.
Frequently asked questions
Which imaging is preferred for suspected pulmonary embolism in pregnancy?
A chest radiograph is performed first, followed by a V/Q scan when the film is normal, because it limits fetal and maternal radiation. CT pulmonary angiography is reserved for abnormal radiographs or indeterminate V/Q results in pulmonary embolism during pregnancy.
Why is D-dimer less useful for pulmonary embolism in pregnancy?
D-dimer rises physiologically in normal pregnancy, so a raised level does not confirm pulmonary embolism. Clinical probability and imaging are therefore used to reach a diagnosis rather than relying on a single raised result.
Which anticoagulant is used for pulmonary embolism during pregnancy?
Weight-adjusted therapeutic low molecular weight heparin is the standard anticoagulant for pulmonary embolism in pregnancy. Warfarin is teratogenic and direct oral anticoagulants are avoided in pregnancy and breastfeeding.
How long should anticoagulation continue after pulmonary embolism in pregnancy?
Anticoagulation for pulmonary embolism in pregnancy continues throughout the pregnancy and for at least six weeks postpartum, with a total duration of at least three months. The exact plan is confirmed by the treating team for each woman.