BACKGROUND: Untreated microangiopathic hemolytic anemia in pregnancy is associated with adverse maternal and perinatal outcomes. Accurate diagnosis is challenging owing to nonspecific clinical features and pathologic findings. Timely initiation of appropriate management is essential to optimize maternal and perinatal outcomes. CASE: A 26-year-old primiparous woman presented at 20 weeks of gestation with new-onset microangiopathic hemolytic anemia on a background of poorly controlled type 1 diabetes. She received eculizumab for presumed atypical hemolytic uremic syndrome. At 24 weeks of gestation, she developed superimposed early-onset preeclampsia; she delivered at 27 weeks of gestation after continuing eculizumab. CONCLUSION: Eculizumab may prolong pregnancy in early-onset preeclampsia. Additional research is needed to assess short-term and long-term maternal and newborn outcomes.