ADAMTS13 and thrombotic thrombocytopenic purpura: TTP during pregnancy can be either a de novo manifestation of disease or a recurrence of a previously known TTP triggered by the pregnant state [46]. Congenital and acquired deficiency of the von Willebrand (vWD) factor cleaving protease (disintegrin and metalloprotease with thrombospondin-1-like domains; ADAMTS13) are considered the hallmark of TTP pathophysiology [47]. The majority of acute cases are acquired, autoantibody-mediated, and are characterized by the presence of anti-ADAMTS13 immunoglobulin G (IgG) antibodies and low ADAMTS13 activity (<10%).