ObjectiveTo characterize perinatal outcomes and long-term maternal complications from thrombotic microangiopathy manifested during pregnancy, and to review the clinical course and long-term follow-up of pregnant women with this condition at our institution over the past 25 years.MethodsWe identified prospectively pregnant women who met clinical and laboratory criteria for thrombotic thrombocytopenic purpura or hemolytic uremic syndrome. Their clinical and laboratory findings, response to treatment, perinatal outcomes, and long-term sequelae were then analyzed.ResultsBetween 1972 and 1997, 11 women had 13 pregnancies complicated by thrombotic microangiopathy, representing an incidence of one per 25,000 births. In three pregnancies (23%), severe and refractory disease developed before midpregnancy. In ten other pregnancies, disease developed either peripartum (62%) or several weeks postpartum (15%). In only two pregnancies with peripartum or postpartum onset of disease was there a clinical picture of severe preeclampsia. In general, the response to treatment was prompt. One woman died of her initial disease in early pregnancy, and mean follow-up of nine survivors was 8.7 years. Disease recurred at least once in 50% of these, two during a subsequent pregnancy. There was at least one serious long-term sequela in all but two survivors; these included recurrence of thrombotic microangiopathy, renal failure, severe hypertension, chronic blood-borne infections, and death.ConclusionThrombotic microangiopathy complicating pregnancy is rare, and with careful evaluation, it should not be confused with atypical preeclampsia. With prompt and aggressive treatment including plasma exchange, the likelihood of immediate survival is high; however, long-term morbidity and mortality are common.