Hemorrhage requiring blood transfusion is a common occurrence in obstetrics. This article reviews each step in the transfusion process, including laboratory preparation of blood, indications for various blood components, complications of blood transfusion, massive transfusion, and alternatives to homologous blood. Current thinking regarding transfusion-related acute lung injury, transfusion-related immunomodulation, early use of plasma for massive transfusion, and the use of adjuvant agents such as activated recombinant factor VII are also discussed.