Many organizations, including The Joint Commission and the National Partnership for Maternal Safety, recommend the use of early warning systems when treating maternity patients. This prospective study evaluated a maternal early warning trigger tool that was internally developed and piloted at six hospitals within a large health system. The tool was pathway specific and targeted the four most common causes of maternal morbidity: hemorrhage, preeclampsia, sepsis, and cardiac dysfunction. Severe maternal morbidity, as defined by the Centers for Disease Control and Prevention, and composite morbidity significantly decreased following implementation of this tool compared with both baseline rates and control hospitals. In 2010, The Joint Commission issued a sentinel event alert on preventing maternal death.