 The WOMAN trial is a large pragmatic randomised double-blind, placebo controlled trial to quantify the effects of the early administration of tranexamic acid on death, hysterectomy and other relevant outcomes. 20,000 adult women, after delivery who have clinically diagnosed postpartum haemorrhage, are eligible if the responsible doctor is for any reason substantially uncertain whether or not to use an antifibrinolytic agent. Additionally, TWO nested studies will be conducted in a subset of women trial participants. The first nested study ETAC aims to evaluate the effect of tranexamic acid TXA on markers of coagulation in 400 women randomised to the WOMAN trial. The second nested study ETAPLAT aims to evaluate the haemostatic effect and antithrombotic effect of TXA in 128 women randomised to the WOMAN trial. 