Background Pregnancy in women with paroxysmal nocturnal hemoglobinuria is rare, with few reports on maternal and fetal mortality rates. DESIGN AND METHODS: A specific questionnaire designed to solicit data on pregnancies in women with paroxysmal nocturnal hemoglobinuria was sent to all members of the French Society of Hematology in January 2008. RESULTS: We identified 27 pregnancies in 22 women at 10 French Society of Hematology centers between 1978 and 2008. The median age was 21.5 years at diagnosis of paroxysmal nocturnal hemoglobinuria and 27 years at pregnancy. None of these women had received eculizumab during their pregnancy. Maternal complications, consisting mostly of cytopenias requiring transfusions, occurred in 95% of cases. Two cases of severe aplastic anemia (de novo in one case and relapse in the other) were recorded. No thrombotic events occurred during pregnancy, whereas 4 postpartum thromboses (16%) were recorded, 2 of which were fatal (maternal mortality rate 8%). Most patients received antithrombotic prophylaxis during pregnancy and postpartum (n=16; 64%). Delivery was preterm in 29% of cases, and birth weight was less than 3 kg in 53% of cases. Fetal mortality rate was 4%. Conclusions Pregnancy during paroxysmal nocturnal hemoglobinuria is associated with increased maternal and fetal mortality rates (8% and 4%, respectively, in this series). Maternal mortality is related to postpartum thromboses. Prophylactic anticoagulation is recommended during pregnancy and for six weeks postpartum.