Background: Thrombotic thrombocytopenic purpura (TTP) is a rare cause of severe thrombocytopenia in pregnancy.
Methods: Six pregnancies in five patients with TTP were followed prospectively over 5 years. Ultralarge von Willebrand factor (ULvWF) multimers and cleaving protease (cp) levels were measured.
Results: TTP relapsed, complicating four of the six pregnancies. Of three patients who relapsed, two had complete or partial vWF-cleaving protease (vWF-cp) deficiency, and one had a normal vWF-cleaving protease level. In all three we found abnormal UL multimers. The two women who did not relapse had normal vWF-cleaving protease level and an absence or loss of UL multimers.
Conclusions: Pregnant patients with a history of TTP must be followed in a tertiary obstetric unit with plasmapheresis available. Influence of vWF-cleaving protease and vWF multimeric abnormalities on TTP relapsing during pregnancy has to be evaluated in a further multicentre study.