糖尿病孕妇之胎儿肩难产的发生率高达10%,巨大儿肩难产的发生率高达25%～50%,当糖尿病孕妇之新生儿实际出生体重≥4000g时,其发生肩难产的危险增加3.6倍。有主张糖尿病孕妇合并巨大儿时行选择性剖宫产,以避免肩难产。但估计胎儿体重来决定分娩方式不准确。为寻找确切的估计胎儿体重的方法,研究2604例妊娠期糖尿病孕妇, The incidence of fetal shoulder dystocia in pregnant women with diabetes is as high as 10%, and the incidence of dystocia in giant shoulders is as high as 25% -50%. When the actual birth weight of newborns with diabetes is ≥4000g, the risk of shoulder dystocia increases by 3.6 times. There is a suggestion that pregnant women with diabetes merge with giant elective cesarean section in order to avoid shoulder dystocia. However, the estimated fetal weight to determine the mode of delivery is not accurate. To find the exact way to estimate fetal weight, 2604 pregnant women with gestational diabetes mellitus,