Pulmonary Embolism in Pregnancy — Special Management

Pulmonary embolism (PE) in pregnancy is a leading cause of maternal morbidity and mortality, accounting for 9-15% of pregnancy-related deaths in developed countries. Pregnancy-related VTE risk increases 4-5 fold throughout gestation and rises to 15-35 fold in the 6 weeks postpartum due to physiologic hypercoagulability (Virchow's triad): increased coagulation factors (II, VII, VIII, X, fibrinogen, vWF), decreased anticoagulant proteins (protein S deficiency, acquired APC resistance), venous stasis from gravid uterus compression of inferior vena cava, and endothelial injury during delivery.

Diagnostic algorithm requires modification due to fetal radiation concerns: 1) Clinical assessment with Wells/Geneva scores (validated in pregnancy with caution); 2) D-dimer interpretation challenging - physiologically rises in pregnancy (especially 3rd trimester), pregnancy-specific cutoffs proposed but not standardized; 3) Bilateral lower extremity compression ultrasound (first-line, no radiation, positive DVT enables treatment without lung imaging); 4) Chest X-ray (low-dose, normal in 84%, helps exclude alternatives); 5) V/Q lung scan (preferred initial test - lower fetal dose 0.07 mGy vs CTPA 0.05-0.6 mGy but higher maternal breast dose vs CTPA); 6) CTPA when V/Q non-diagnostic or unavailable.

Treatment is low-molecular-weight heparin (LMWH, enoxaparin 1 mg/kg subcutaneously BID adjusted by anti-Xa levels in selected cases) - first-line throughout pregnancy and 6 weeks postpartum due to no placental crossing, lower bleeding risk than UFH, and outpatient administration. Warfarin contraindicated in pregnancy (fetal warfarin syndrome 6-12 weeks, fetal CNS abnormalities, fetal bleeding 3rd trimester) but safe postpartum and during breastfeeding. DOACs (rivaroxaban, apixaban, dabigatran) avoided due to insufficient pregnancy data. UFH for severe renal failure or imminent delivery (rapid reversal). Peripartum: LMWH stop 24 hours before planned delivery, regional anesthesia 24 hours after last therapeutic dose.