How to manage pulmonary embolism (PE) in a pregnant woman?

Management of Pulmonary Embolism in Pregnancy

Immediately initiate therapeutic-dose low molecular weight heparin (LMWH) at weight-based dosing (using early pregnancy weight) for any confirmed or highly suspected pulmonary embolism in pregnancy, continuing throughout the entire pregnancy and for at least 6 weeks postpartum (minimum 3 months total duration). 1, 2, 3

Diagnostic Approach

Proceed with formal diagnostic imaging without hesitation—both CT pulmonary angiography (CTPA) and ventilation-perfusion (V/Q) scanning are safe in pregnancy and accurate diagnosis is mandatory before committing to prolonged anticoagulation. 4, 2

• Start with clinical probability assessment using validated prediction rules or clinical judgment 2
• Measure D-dimer in low or intermediate probability cases to potentially avoid imaging 2
• Perform compression ultrasound of legs if DVT symptoms present, as this avoids radiation and confirms venous thromboembolism 2
• Use CTPA or V/Q scan when imaging is needed—both carry minimal fetal radiation risk (0.003-0.13 mGy for CTPA, 0.06-0.2 mGy for V/Q) 4

Initial Anticoagulation Strategy

For Hemodynamically Stable PE (Most Cases)

Start therapeutic LMWH immediately based on early pregnancy weight, not current weight, using standard fixed-dose regimens (e.g., enoxaparin 1 mg/kg subcutaneously twice daily). 1, 2, 3

• LMWH does not cross the placenta and carries minimal fetal risk 1
• Anti-Xa monitoring is generally unnecessary except at extremes of body weight or with renal disease 1
• Continue LMWH throughout entire pregnancy without switching to oral agents 1, 2

For Hemodynamically Unstable PE (High-Risk)

Initiate intravenous unfractionated heparin (UFH) with weight-adjusted bolus (80 units/kg) followed by continuous infusion (18 units/kg/hour), then transition to LMWH once stabilized. 1, 2, 3

• UFH allows rapid reversal if needed and easier peripartum management 2
• For truly life-threatening PE with shock or cardiac arrest, thrombolysis should be administered despite pregnancy 1, 3, 5

Absolutely Contraindicated Medications

NOACs (apixaban, rivaroxaban, dabigatran, edoxaban) are absolutely contraindicated throughout pregnancy and lactation—discontinue immediately if patient was taking them. 1, 2, 3

Warfarin is teratogenic in the first trimester (causing embryopathy) and causes fetal/neonatal hemorrhage in the third trimester—never use during pregnancy. 4, 1

• Some older guidelines suggested cautious warfarin use in second trimester by analogy to mechanical valve patients, but this should be avoided whenever possible 4

Peripartum Management (Critical for Safety)

Discontinue LMWH at onset of regular uterine contractions or 24 hours before planned delivery. 4, 1, 3

Do not place epidural or spinal needle within 24 hours of last therapeutic LMWH dose to prevent spinal hematoma. 1, 2, 3

• For high-risk PE near delivery, convert LMWH to UFH infusion at least 36 hours before anticipated delivery 2
• Stop UFH infusion 4-6 hours before expected delivery time 4, 2
• Some protocols use low-dose UFH (5000 units IV every 12 hours) during labor, though this remains debated 4

Postpartum Anticoagulation

Resume LMWH 4-12 hours after vaginal delivery (or 12-24 hours after cesarean section), depending on bleeding risk and epidural catheter removal timing. 1, 3

• Transition to warfarin postpartum if desired—warfarin is safe during breastfeeding 4, 1, 2
• Continue anticoagulation for minimum 3 months total duration, with at least 6 weeks postpartum 1, 2, 3

Management of Life-Threatening PE

For massive PE with hemodynamic instability (shock, cardiac arrest), administer systemic thrombolysis despite pregnancy—maternal survival is 94% with this approach. 1, 5, 6

• Use alteplase (rtPA) 100 mg over 2 hours, or streptokinase if alteplase unavailable 4
• Thrombolytics do not cross the placenta 4
• Major bleeding risk is 17.5% during pregnancy but 58% in postpartum period (primarily postpartum hemorrhage) 6
• Fetal death occurs in approximately 12% of cases following maternal thrombolysis 1, 6

Avoid thrombolysis in the peripartum period (active labor through 24 hours postpartum) unless the patient is literally dying—consider catheter-directed thrombectomy or surgical embolectomy instead if available. 1, 3, 5, 6

• Catheter-directed embolectomy is emerging as preferred option for peripartum massive PE due to lower bleeding risk 7, 6
• Surgical embolectomy has 86% maternal survival but 20% major bleeding risk 6
• IVC filter placement follows same indications as non-pregnant patients (contraindication to anticoagulation, recurrent PE despite adequate anticoagulation) 4

Critical Pitfalls to Avoid

Never underdose LMWH due to bleeding concerns from threatened miscarriage—PE poses immediate life-threatening maternal risk that supersedes bleeding concerns. 1

Never place epidural within 24 hours of therapeutic LMWH—this causes spinal hematoma with permanent paralysis. 1, 2, 3

Never continue NOACs during pregnancy thinking they are safer than heparin—they are teratogenic and contraindicated. 1, 2, 3

Never use thrombolysis during active labor or immediate postpartum unless truly life-threatening—bleeding risk is 58% in this window. 1, 6

Multidisciplinary Coordination

Mandatory involvement of obstetrics, maternal-fetal medicine, hematology/thrombosis service, and anesthesiology for coordinated care planning, particularly around delivery timing and epidural management. 1, 2, 3

• Plan delivery timing in advance when possible to optimize anticoagulation management 4
• Ensure 24/7 availability of interventional options (catheter-directed therapy, surgical embolectomy, ECMO) for high-risk cases 5, 6