What is the recommended treatment for a 20-week pregnant woman with pulmonary embolism (PE)?

Treatment of Pulmonary Embolism in a 20-Week Pregnant Woman

Low molecular weight heparin (LMWH) is the recommended treatment for pulmonary embolism (PE) in a 20-week pregnant woman and should be administered throughout the entire pregnancy. 1

Diagnostic Confirmation

Before initiating treatment, confirm the diagnosis of PE using appropriate imaging:

• D-dimer testing can be used initially, though values physiologically increase during pregnancy (still, a normal result has good negative predictive value) 1
• If D-dimer is elevated or clinical suspicion remains high:
  • Lower limb compression ultrasonography (CUS) should be performed first, as a positive result would confirm thromboembolism and avoid radiation exposure 1
  • If CUS is negative, proceed with either:
    • Perfusion lung scan (radiation exposure 0.06-0.12 mSv) 1
    • CT pulmonary angiography with low-radiation protocol (radiation exposure 0.008-0.08 mSv in second trimester) 1

Treatment Protocol

Acute Phase Treatment

1. Initial anticoagulation:

   • Start weight-adjusted LMWH immediately upon diagnosis 1
   • Dosing options:
     • LMWH 200 IU/kg once daily or 100 IU/kg twice daily 1
     • Example: Dalteparin or enoxaparin (most studied in pregnancy) 2

2. Monitoring:

   • Anti-Xa monitoring may be considered in women with:
     • Extremes of body weight
     • Renal disease
     • When otherwise clinically indicated 1
   • Routine monitoring is generally not required 1

Long-term Management

• Continue LMWH throughout the entire pregnancy 1

• Avoid vitamin K antagonists (warfarin) as they:

  • Cross the placenta
  • Are associated with embryopathy during first trimester
  • Can cause fetal/neonatal hemorrhage and placental abruption in third trimester
  • May cause central nervous system anomalies in any trimester 1, 3

• Avoid fondaparinux due to lack of data in pregnancy 1

• Avoid direct oral anticoagulants (NOACs) as they are contraindicated during pregnancy 1

Peripartum Management

1. Labor and delivery planning:

   • Discontinue LMWH at onset of regular uterine contractions 1
   • For planned delivery, discontinue LMWH at least 24 hours before 1
   • If epidural analgesia is desired, LMWH must be discontinued at least 24 hours prior to insertion of epidural needle 1

2. Postpartum management:

   • Resume LMWH 12-24 hours after delivery or epidural catheter removal 1
   • Continue anticoagulation for at least 6 weeks postpartum with a minimum total treatment duration of 3 months 1
   • May transition to vitamin K antagonists postpartum (safe during breastfeeding) 1

Special Considerations

High-Risk PE

• For massive, life-threatening PE:
  • Thrombolytic therapy should be considered only in critical cases when the patient is likely to die and surgical embolectomy is not immediately available 1
  • Thrombolytic agents do not cross the placenta but carry an 8% risk of maternal bleeding, usually from the genital tract 1

Multidisciplinary Approach

• Close collaboration between obstetrician, anesthesiologist, and attending physician is essential for optimal management 1

Common Pitfalls to Avoid

1. Using vitamin K antagonists during pregnancy, especially in first and third trimesters
2. Failing to adjust LMWH dosing for pregnant women with extremes of body weight
3. Not planning appropriately for labor and delivery anticoagulation management
4. Insufficient duration of anticoagulation postpartum (should continue for at least 6 weeks)
5. Inadequate communication between obstetric, anesthetic, and medical teams

By following these guidelines, you can effectively manage PE in a 20-week pregnant woman while minimizing risks to both mother and fetus.