Low antithrombin activity before delivery predicts subsequent hypertensive disorders in pregnancy.

<bold>Objective: </bold>To examine whether laboratory parameters can predict the onset of recurrent hypertensive disorders of pregnancy (HDP).<bold>Methods: </bold>A retrospective study of 257 women with consecutive deliveries at a hospital in Sapporo, Japan, between 2009 and 2017. Women were divided into four groups according to whether or not they had HDP in the first and second peripartum periods (HDP-HPD, HDP-Non, Non-HDP, Non-Non). HDP was defined as gestational hypertension and/or proteinuria. Laboratory parameters measured on the day of or 1 day before delivery were compared between peripartum-1 and peripartum-2.<bold>Results: </bold>Frequency of HDP in peripartum-2 was higher among the 24 (9.3%) women with HPD in peripartum-1 (6/24, 25.0%) than among the 233 (90.7%) women without (3/233, 1.3%) (P<0.001). In peripartum-1, women with HDP had lower median antithrombin activity than those without (74% vs 89%, P=0.021). Antithrombin activity in peripartum-1 was also lower in the HDP-HDP (67%) than in the HDP-Non (79%) group (P=0.021). Antithrombin activities of 77% or less at the first delivery predicted HDP in peripartum-1 (P<0.001) and 70% or less predicted HDP in peripartum-2 (P=0.018).<bold>Conclusion: </bold>Women with HDP in peripartum-1 had a higher incidence of HDP recurrence. Low antithrombin before a first delivery might predict recurrent HDP in a second pregnancy. [ABSTRACT FROM AUTHOR]