在穿刺羊膜囊前作超声波检查,确定胎盘,胎儿位置,可以减少产前遗传学检定的危险性,而增加其准确性。材料和方法为了遗传学鉴定,在妊娠14-16周间,作超声检查。检查前先给妇女大量饮水,以使小便能充盈膀胱。妇女平卧,在下腹先作上下间、再作左右间 Ultrasound in the puncture amniotic sac before ultrasound to determine the placenta, fetal position, can reduce the risk of prenatal genetic testing, and increase its accuracy. Materials and Methods For genetic identification, ultrasound was performed between 14 and 16 weeks of gestation. Give women a large amount of water before checking so that urine can fill the bladder. Women supine, in the lower abdomen before the upper and lower room, and then for the left and right