Relationship between antithrombin activity and interval from diagnosis to delivery among pregnant women with early-onset pre-eclampsia

Objective: To determine the cutoff of antithrombin activity for predicting the interval from diagnosis of early-onset pre-eclampsia to delivery. Methods: At Hokkaido University Hospital, Japan, data were retrospectively assessed on antithrombin activity measured at both diagnosis of pre-eclampsia and delivery among women with singleton pregnancy and pre-eclampsia (defined by combined gestational hypertension and proteinuria) between 2009 and 2017. The timing of delivery was determined by maternal and fetal well-being. Results: Among 2904 singleton deliveries, antithrombin activity was measured for 94 (3.2%) women diagnosed with pre-eclampsia. The median (range) interval was significantly longer for 38 (40%) women with early-onset than for 56 (60%) women with late-onset pre-eclampsia (6.5 [0–27] vs 1 [0–29] days, respectively; P<0.001). In the early-onset group, median antithrombin activity at diagnosis was significantly lower for 19 women with an interval of less than 7 days (72% [60%–92%]) than for 19 women with a longer interval (≥7 days) (84% [59%–110%]; P=0.012). Antithrombin activity of 78% at diagnosis of early-onset pre-eclampsia was optimal for predicting a delivery interval of less than 7 days. Conclusion: A cutoff of 78% antithrombin activity at diagnosis of early-onset pre-eclampsia might be used as a predictor of delivery within 7 days.