Objective To examine the effect of cord around neck to the umbilical arterial blood flowing indexes,PI,RI and S/D,and point out the most appropriate time for transmitting oxygen.

• 目的检查胎儿脐带绕颈对脐动脉动力学指标:搏动指数(PI)、阻力指数(RI)、收缩期血流峰值/舒张期血流峰值(S/D)的影响,探讨脐带绕颈是引起胎儿宫内缺氧的主要原因,并指出给氧的最佳时机。