Enrollment of the study population. From 2000-2010, 592 consecutive patients with an adulthood-onset TTP related to a severe ADAMTS13 functional deficiency were prospectively enrolled in the French registry for Thrombotic Microangiopathies. A total of 417 patients were women; 280 were less than 45 years of age (67%). In 48 of those latter women, 1 or several TTP boots were associated with pregnancy (n = 40) or the postpartum period (n = 8). Six women had already experienced TTP boots before their pregnancy-associated TTP, whereas pregnancy accounted for the first TTP episode in 42 women.