Methods:Acceleration time(AT) of fetal umbilical artery and cerebral artery were detection by color Doppler image in 144 cases normal fetuses divided to 7 groups by their gestational age.

• 方法:彩色多普勒测定144例正常胎儿(按孕龄分为7组)脐动脉、脑动脉加速时间,用方差分析和t检验进行组间比较。