Flowchart of the enrollment of patients with pregnancy-onset TTP in the cohort study. From 1 January 2000 to 30 September 2020, 1174 patients with pregnancy onset-TMA were enrolled and investigated for ADAMTS13. In total, 108 patients had a severe functional deficiency in ADAMTS13 (activity of <10 IU/dL) and were subsequently diagnosed with pregnancy-onset TTP. Of those 108 patients, 52 had iTTP (anti-ADAMTS13 IgG of >15 U/mL), 27 had uTTP (anti-ADAMTS13 IgG of <15 U/mL), and 29 had cTTP.