Methods:The blood flow impedance of fetal UA,MCA such as the peak-systolic/diastolic ratio(S/D),pulse index(PI) and resistance index(RI) were measured by color Doppler ultrasound.

• 方法:应用彩色多普勒超声胎儿监测脐动脉、大脑中动脉S/D、PI、RI等血流指标。