Clinical features of women with thrombotic microangiopathy in pregnancy: A case series from a single Japanese tertiary perinatal care center

Aim Although perinatal thrombotic microangiopathy has become increasingly understood, the racial characteristics of patients with this condition remain unclear. Herein, we report the characteristics of patients with perinatal thrombotic microangiopathy at a single institution in Japan. Methods We conducted a retrospective study over a 5‐year period from January 1, 2017, to December 31, 2021, using the electronic medical records of pregnant women who delivered at the perinatal center of our hospital. We extracted the data of those who developed perinatal thrombotic microangiopathy and evaluated their characteristics at the time of disease onset, final diagnosis, and maternal and fetal outcomes. Results Of the 10 224 deliveries that occurred during the 5‐year period, only seven patients (0.06%) had perinatal thrombotic microangiopathy. The median pre‐pregnant body mass index was 18.65 kg/m2 (minimum 17.3 kg/m2, maximum 20.7 kg/m2). More than half of the patients were conceived by in‐vitro fertilization, and 42% these had twin deliveries. Four patients had a history of rheumatic disease. The other three patients without underlying diseases developed thrombotic microangiopathy with HELLP syndrome, and one patient transitioned to atypical hemolytic uremic syndrome. Conclusions Based on low body mass index and in‐vitro fertilization, which are characteristic of Japanese women, medical complications and twin pregnancies may be a risk for thrombotic microangiopathy. Additionally, depending on the cause of thrombotic microangiopathy, its timing and onset differed.