Effects of anti-Xa activity monitoring on the outcome of high-risk pregnancies treated with a prophylactic dose of low-molecular-weight heparin.

Abstract

To evaluate if anti-Xa level monitoring and dose adjustment in women using a prophylactic dose of enoxaparin can decrease placenta-mediated pregnancy complications. This retrospective observational cohort study included pregnant women receiving enoxaparin prophylaxis, who were followed at the Thrombosis and Hemostasis Outpatient clinic between 2010 and 2017. The dose was adjusted according to enoxaparin anti-Xa levels in the study group or the weight of individuals in the control group. Of 585 women surveyed, 110 met the inclusion criteria; 63 of them were included in the study group and 47 in the control group. Mean starting dose was 46 versus 43 mg (p = .25), mean final dose was 52 mg versus 45 mg (p = .03) and dose adjustment was required in 37% versus 11% (p = .002) in the study and control groups, respectively. Twenty-eight percent of anti-Xa measurements in the second trimester were beneath the prophylactic threshold, compared to 11% and 16% in the first and third trimesters, respectively (p = .02). Labors ended with live birth in 91% versus 94% of cases (p = .5), 85% versus 68% of pregnancies were term (p = .05), 11% versus 23% of newborns were low birth weight (p = .1) and placenta-mediated pregnancy complications were documented in 9% versus 19%, (p = .17) in the study group relative to controls, respectively. The most prominent decrease in anti-Xa levels was observed in the second trimester. Monitored women had significantly more term deliveries and demonstrated a trend toward higher birth weight and fewer placenta-mediated pregnancy complications. Larger studies are needed to confirm improved pregnancy outcome in monitored women.