Prophylactic and therapeutic enoxaparin during pregnancy: indications, outcomes and monitoring

OBJECTIVES: To evaluate the efficacy and safety of prophylactic and therapeutic enoxaparin in pregnancy. STUDY DESIGN: Three-year prospective audit. SETTING: Tertiary level obstetric hospital. POPULATION: Fifty-two women who received subcutaneous enoxaparin, either a prophylactic dose (40 mg daily) in 26 pregnancies or therapeutic dose (1 mg/kg twice daily) in 32 pregnancies. MATERIALS AND METHODS: Pregnant women treated with enoxaparin were prospectively entered into a register. Data were retrieved by case note review. MAIN OUTCOME MEASURES: Pregnancy outcomes, treatment complications and anti-Xa levels. RESULTS: In the prophylactic group there were no fetal losses, thromboembolic events or complications related to enoxaparin. In the therapeutic group there were four first trimester miscarriages, a termination and 27 live births. Therapeutic enoxaparin prevented further thromboembolism without complications. One woman was treated with intermediate dose enoxaparin when she presented at 5 weeks' gestation on warfarin and 7 weeks after a venous thromboembolism. She developed a recurrent pulmonary embolus 3 weeks later and was subsequently treated with therapeutic enoxaparin. In the therapeutic group the enoxaparin dose/kg correlated poorly with anti-Xa levels, and dose adjustments were made. Therapeutic mean (SD) trough and peak anti-Xa levels were 0.33 U/mL (0.14) and 0.86 U/mL (0.24) in the first trimester and 0.48 U/mL (0.19) and 0.84 U/mL (0.23) in the third trimester. CONCLUSIONS: In the present series, prophylactic and therapeutic enoxaparin treatment during pregnancy was effective and safe. Studies are required to determine the optimal duration of treatment with therapeutic enoxaparin following venous thromboembolism in pregnancy and the clinical relevance of anti-Xa monitoring.