A review of pregnancy-associated thrombotic thrombocytopenic purpura (TTP) in 166 pregnancies was undertaken using 92 English-language publications from 1955 to 2006. Initial and recurrent TTP presents most often in the second trimester (55.5%) after 1-2 days of signs/symptoms; postpartum TTP usually occurs following term delivery. TTP with preeclampsia (n = 28) exhibits 2-4 times higher aspartate aminotransferase (AST) values and lower total lactate dehydrogenase (LDH) to AST ratios (LDH to AST ratio = 13:1), compared with TTP without preeclampsia (LDH to AST ratio = 29:1). Maternal mortality is higher with initial TTP (26% vs 10.7%), especially with concurrent preeclampsia (44.4% vs 21.8%, P < .02). Although maternal mortality with TTP has substantially declined when plasma therapy is utilized, delay of diagnosis and therapy for initial TTP confounded by preeclampsia/hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome remains a significant maternal-perinatal threat. Rapid and readily available laboratory testing to quickly diagnose TTP and HELLP syndrome/preeclampsia is desperately needed to improve care.