What is the management of pulmonary embolism (PE) in pregnant women?

Management of Pulmonary Embolism in Pregnancy

Low-molecular-weight heparin (LMWH) administered as therapeutic fixed doses based on early pregnancy weight throughout the entire pregnancy is the anticoagulant of choice for PE in pregnancy, with thrombolysis reserved exclusively for life-threatening, high-risk PE with hemodynamic instability. 1, 2

Diagnostic Algorithm

Initial Assessment

• Begin with chest radiograph (CXR) as the first radiation-associated procedure in all pregnant women with suspected PE 3, 1
• If leg symptoms are present, perform venous compression ultrasonography (CUS) of lower extremities first—a positive result warrants immediate anticoagulation and eliminates the need for thoracic imaging 1, 2
• Measure D-dimer despite pregnancy: approximately 50% of women have normal D-dimer at 20 weeks gestation, and a normal result has the same exclusion value as in non-pregnant patients 3, 1

Imaging Strategy Based on CXR Results

If CXR is normal:

• Proceed with lung scintigraphy (V/Q scan) as the next imaging test rather than CTPA to minimize maternal breast radiation exposure 3, 1
• All radiation doses from diagnostic tests fall well below the 50 mSv fetal safety threshold 3

If CXR is abnormal:

• Proceed with CTPA as the next imaging test rather than lung scintigraphy 3

If V/Q scan is nondiagnostic:

• Perform CTPA for definitive diagnosis rather than clinical management alone 3

Anticoagulation Treatment

Standard Management (Non-High-Risk PE)

Primary therapy:

• LMWH is the anticoagulant of choice, dosed based on early pregnancy weight and continued throughout the entire pregnancy 1, 2
• Weight-adjusted dosing should be used, with anti-Xa monitoring considered at extremes of body weight, with renal disease, or when clinically necessary 1
• Neither LMWH nor unfractionated heparin (UFH) cross the placenta or appear in breast milk 1

Absolute contraindications:

• Vitamin K antagonists (VKAs) are contraindicated during pregnancy 1
• NOACs (including apixaban, rivaroxaban, dabigatran) are explicitly contraindicated during pregnancy and lactation 3, 1, 2

High-Risk PE Management

Indications for advanced therapy:

• Thrombolysis or surgical embolectomy should be considered only for high-risk PE with shock or cardiac arrest 1, 2, 4
• UFH is the preferred acute anticoagulant in high-risk PE requiring potential thrombolysis 1

Thrombolysis outcomes:

• Published cases show 94% maternal survival (95% CI, 86-98%) with thrombolysis for massive PE 5
• Major bleeding risk is 17.5% during pregnancy but increases dramatically to 58.3% in the postpartum period, primarily from severe postpartum hemorrhages 5
• Fetal deaths possibly related to PE treatment occur in 12.0% of cases treated during pregnancy 5

Critical timing consideration:

• Thrombolytic treatment should not be used peri-partum except in life-threatening PE settings 1, 2
• About half of severe postpartum PEs occur within 24 hours of delivery 5

Peripartum Anticoagulation Management

Timing of Anticoagulation Discontinuation

For planned delivery:

• Strong consideration should be given to planned delivery in collaboration with a multidisciplinary team to avoid spontaneous labor while fully anticoagulated 1
• ≥24 hours must elapse since the last therapeutic LMWH dose before spinal or epidural needle insertion 1, 2
• For high-risk situations, convert LMWH to UFH infusion ≥36 hours prior to delivery 1
• Stop UFH infusion 4-6 hours prior to anticipated delivery and ensure activated partial thromboplastin time is normal before regional anesthesia 1, 2

For spontaneous labor:

• LMWH should be discontinued at the onset of regular uterine contractions 2

Regional Anesthesia Safety

• Do not administer LMWH for ≥4 hours after epidural catheter removal 1
• Activated partial thromboplastin time must be normal prior to regional anesthesia if UFH was used 1, 2

Postpartum Anticoagulation

Duration and agent selection:

• Continue anticoagulation for ≥6 weeks after delivery with a minimum overall treatment duration of 3 months 1, 2
• LMWH may be replaced by VKAs after delivery 1, 2
• Both LMWH and warfarin can be given to breastfeeding mothers 1, 2
• NOACs are not recommended postpartum during breastfeeding 1, 2

Critical Pitfalls to Avoid

Diagnostic errors:

• Do not delay diagnostic imaging due to radiation concerns—all modalities deliver fetal radiation doses well below safety thresholds 3, 1
• Avoid overdiagnosis of PE, which has lifelong implications including bleeding risk during delivery, contraindications to estrogen contraception, and thromboprophylaxis requirements in future pregnancies 1, 2

Treatment errors:

• Never use thrombolysis for intermediate-risk PE—reserve only for life-threatening hemodynamic instability 1, 2, 4
• Never administer regional anesthesia within 24 hours of therapeutic LMWH, which risks spinal hematoma 1, 2
• Never prescribe NOACs during pregnancy or lactation 3, 1, 2

Risk stratification errors:

• Do not use PESI or sPESI scores in pregnant women, as physiological pregnancy changes (fall in blood pressure, rise in heart rate, subjective breathlessness) will overestimate risk 3

Multidisciplinary Approach

• All pregnant and postpartum women with suspected or confirmed PE should be reviewed by a consultant and discussed with maternity services prior to discharge 3
• A multidisciplinary pregnancy heart team should collaborate in planning ante-, peri-, and postpartum care pathways 1, 2