METHOD: Ultrasonic examination was conducted in 3 546 middle and late pregnant women to check structure of head,biparietal diameter(BPD) , cervicosa-cral diameter(CSD)and amount of amniotic fluid.

• 方法:应用B超检查3 564例中、晚期妊娠妇女胎儿的各个部位和器官,测量胎头双顶径(BPD)、胎儿脊柱颈骶径(CSD)及羊水池深。