They received ultrasound scan at about 28th weeks and 38th weeks to measure fetal head circumference(HC),abdomen circumference(AC),femoral bone,humeral bone length(FL,HL)and biparietal diameter(BPD).

• 于妊娠28周及38周左右行两次B超检查,测量胎儿双顶径、头围、腹围、股骨及肱骨长度,并用两次测量之差值反映胎儿孕晚期的生长情况。