Evaluation of therapeutic enoxaparin in a pregnant population at a tertiary hospital

Background Therapeutic anticoagulation with enoxaparin in pregnancy is complex due to varying pharmacokinetics and the increasing prevalence of obesity. There is limited evidence to support current dosing and monitoring strategies of enoxaparin in this population. Aim To describe the current practice in therapeutic anticoagulation in the pregnant population at a tertiary institution. Methods A retrospective study of pregnant women on therapeutic enoxaparin between January 2007 and December 2011. Results Forty‐four pregnant women requiring therapeutic anticoagulation were identified and divided into two groups, monitored with anti‐factor Xa (AXA) concentrations and unmonitored. Fifty‐five percent of monitored women were initiated on the recommended 1 mg/kg twice a day (bd) enoxaparin dose‐strategy. Eighty‐two percent of women were monitored; however, there was variability regarding the timing, frequency and subsequent dose adjustments from monitoring. Overall, as pregnancies progressed, there was both increasing dose adjustments and increasing frequency of monitoring. Fourteen women had a BMI over 30 kg/m2, and 13 of these women were monitored. Nine monitored obese women required doses less than 1 mg/kg/bd to maintain a therapeutic AXA level. Management appeared to be individualised. There were small numbers of toxicity events. Conclusion Variation exists in dosing and monitoring practices for therapeutic enoxaparin in the pregnant population. Dosing obese patients using 1 mg/kg twice daily can lead to toxic AXA concentrations, and dose reductions are required to maintain a therapeutic range. A larger prospective study reviewing dose, AXA concentrations and outcome data is necessary to make dosing recommendations in this group.