It is a multicenter randomized, double-blind and placebo-controlled trial. Totally 6500 women to delivery by cesarean section will be recruited in this study. In addition to routinely oxytocin, the women in study group will receive TXA 1 g in 2 minutes after they delivered their babies, and those in control group will receive placebo. The incidence of postpartum hemorrhage, the amount of bleeding, as well as the side effects will be observed.