Low antithrombin activity before delivery predicts subsequent hypertensive disorders in pregnancy

Objective To examine whether laboratory parameters can predict the onset of recurrent hypertensive disorders of pregnancy ( HDP ). Methods 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. Results 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). Conclusion 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.