What hematology lab workup is required for pregnant women needing Lovenox (enoxaparin) due to pregnancy-related issues?

Hematology Lab Workup for Pregnant Women Requiring Lovenox

For pregnant women requiring Lovenox (enoxaparin) therapy, a comprehensive thrombophilia workup should be performed, including anti-Factor Xa levels for monitoring therapeutic dosing, complete blood count with platelets, and coagulation studies to ensure safe and effective anticoagulation management. 1

Initial Baseline Testing

• Complete Blood Count (CBC) with platelets

  • Essential to establish baseline hemoglobin and platelet count
  • Monitors for heparin-induced thrombocytopenia (HIT), which is rare with LMWH but still possible 1

• Coagulation Studies

  • Prothrombin Time (PT)
  • Activated Partial Thromboplastin Time (aPTT)
  • International Normalized Ratio (INR) if transitioning from/to warfarin

• Renal Function Tests

  • Serum creatinine and BUN
  • Creatinine clearance (enoxaparin is renally cleared and dosing may need adjustment in renal impairment)

Thrombophilia Testing

Based on indication for Lovenox, testing for inherited and acquired thrombophilias may be necessary:

• Inherited Thrombophilias

  • Factor V Leiden mutation (PCR testing and activated Protein C resistance assay) 2
  • Prothrombin gene mutation (G20210A)
  • Protein C activity and antigen
  • Protein S activity and antigen
  • Antithrombin activity
  • Homocysteine levels

• Acquired Thrombophilias

  • Antiphospholipid antibodies:
    • Lupus anticoagulant
    • Anticardiolipin antibodies (IgG, IgM)
    • Anti-β2 glycoprotein I antibodies (IgG, IgM)

Monitoring Tests During Lovenox Therapy

• Anti-Factor Xa Levels

  • Critical for monitoring therapeutic dosing
  • Should be measured 4-6 hours after morning dose 1
  • Target levels:
    • For prophylactic dosing: 0.2-0.6 U/mL
    • For therapeutic dosing: 0.7-1.2 U/mL 1
  • Frequency:
    • Initially weekly until stable
    • Then monthly or with any significant weight change
    • More frequent monitoring in third trimester due to increased heparin-binding proteins 1

• Periodic CBC with Platelets

  • Monitor every 1-2 weeks during first month
  • Then monthly to assess for thrombocytopenia

Special Considerations

• For Mechanical Heart Valves

  • More intensive monitoring with anti-Xa levels twice weekly initially 1
  • Consider adding low-dose aspirin (75-100 mg daily) in second and third trimesters 1

• For Recurrent Pregnancy Loss with Thrombophilia

  • Complete thrombophilia panel as above
  • Consider additional testing for other causes of pregnancy loss 3

• For Treatment of Acute VTE

  • D-dimer levels (baseline)
  • Consider imaging studies as clinically indicated

Pre-Delivery Testing

• Anti-Factor Xa level within 1 week before planned delivery
• CBC with platelets within 24-48 hours before delivery
• Coagulation studies (PT/aPTT) if considering neuraxial anesthesia

Pitfalls to Avoid

• Failure to adjust dosing with weight changes during pregnancy
• Inadequate monitoring of anti-Xa levels, especially in high-risk patients with mechanical heart valves
• Discontinuing Lovenox too late before delivery (should be stopped 12-24 hours before planned delivery) 1
• Not recognizing combined thrombophilias which significantly increase VTE risk and may require higher dosing 2

By following this comprehensive laboratory workup, clinicians can optimize the safety and efficacy of Lovenox therapy during pregnancy, minimizing risks of both thrombosis and bleeding complications.