Enoxaparin treatment in women with mechanical heart valves during pregnancy

OBJECTIVE: This prospective audit reports pregnancy outcomes, anticoagulati on complications, and anti-Xa levels in women with mechanical heart valves who were treated with therapeutic enoxaparin plus aspirin during pregnancy. STUDY DESIGN: Between 1997 and 1999, 11 women with mechanical heart valves were treated with enoxaparin, 1 mg/kg twice daily, and aspirin, 100 to 150 mg daily during 14 pregnancies. Predose and 4-hour postdose anti-Xa levels were monitored monthly. RESULTS: There were 9 live births, 3 miscarriages, and 2 terminations. In 4 8 months of enoxaparin treatment, one woman who had a documented valve thro mbosis when she presented at 8 weeks' gestation also had a valve thrombosis at 20 weeks' gestation. There were no enoxaparin-related hemorrhagic compl ications. Mean (SD) anti-Xa levels were 0.46 (0.12) U/mL predose and 0.89 ( 0.22) U/mL 4 hours postdose. CONCLUSION: Successful pregnancy outcome may be achieved with therapeutic s ubcutaneous enoxaparin, but its efficacy at preventing valve thrombosis rem ains uncertain. Further data are required before use of enoxaparin during p regnancy in women with mechanical heart valves can be recommended.