【Abstract】 The obstetrical patients with critical situation, such as pregnancy with heart disease, severe preeclampsia, are increasing day by day. Standard ASA monitoring is not sufficient for these patients. The application of traditional hemodynamic monitoring was limited due to the injury and complications. The hemodynamic monitoring has gradually changed from being invasive to minimally invasive and noninvasive. The cardiac output measured by noninvasive hemodynamic monitoring device, noninvasive cardiac output monitoring (NICOM), based on chest bioreactance has good correlation with pulmonary artery catheter. Moreover，noninvasive cardiac output monitoring can predict the evolution of uteroplacental diseaseresults and has unique advantages in critical obstetrics. In this paper, it intends to be a briefly review on principles, methods, indications，advantages and disadvantages of NICOM and its clinical application in critical obstetrics.