Changes in VWF and blood volume during pregnancy, and proposed clinical trial. (A) VWF:RCo level during pregnancy. von Willebrand ristocetin cofactor activity in VWD treated patients (in red), in VWD untreated patients, and in pregnant controls. Adapted from James et al.⁷  (B) Blood volume during pregnancy. Blood volume (blue line) increases 1.5-fold by the eighth month of pregnancy, compared with baseline. Adapted from Liu and Arany.¹⁸  (C) PREVENT PPH in VWD trial schema. This is the schema for Prevent Postpartum Hemorrhage in von Willebrand Disease, or PREVENT PPH in VWD, a prospective, randomized, controlled trial in women with VWD. Adapted from Machin et al.²⁵