孕产妇死亡率逐年下降，但是产后出血仍是主要原因。产后出血的风险评估包括高危因素的识别和风险评估工具的使用，但现有手段仍有其局限的地方。同时，还需要实时对产后出血进行预警，常用指标包括出血量、失血速度、生命体征、休克指数等，同时基于这些指标构建实用的产后出血预警系统。

Although the maternal mortality has decreased year by year，postpartum hemorrhage（PPH）is still the main reason for maternal death. The risk assessment of PPH includes recognition of high risks and the application of the assessment tools.The existing methods have their limitations，and it's necessary to use the bleeding volume，speed of blood loss，vital signs and shock index for the early warning of postpartum hemorrhage in real time，and we can establish the early warning system with these indexes.