Summary. Background: Postpartum hemorrhage (PPH) is a major source of maternal morbidity. Objectives: This study's objective was to determine whether changes in hemostasis markers during the course of PPH are predictive of its severity. Patients and methods: We enrolled 128 women with PPH requiring uterotonic prostaglandin E2 (sulprostone) infusion. Two groups were defined (severe and non-severe PPH) according to the outcome during the first 24 hours. According to our criteria, 50 of the 128 women had severe PPH. Serial coagulation tests were performed at enrollment (H0), and 1, 2, 4 and 24 hours thereafter. Results: At H0, and through H4, women with severe PPH had significantly lower fibrinogen, factor V, antithrombin activity, protein C antigen, prolonged prothrombin time, and higher D-dimer and TAT complexes than women with non-severe PPH. In multivariate analysis, from H0 to H4, fibrinogen was the only marker associated with the occurence of severe PPH. At H0, the risk for severe PPH was 2.63-fold higher for each 1 gL−1 decrease of fibrinogen. The negative predictive value of a fibrinogen concentration >4 gL−1 was 79% and the positive predictive value of a concentration ≤2 gL−1 was 100%. Conclusion: These findings indicate that a simple fibrinogen measurement can anticipate the risk of severe bleeding in PPH.