33周羊水指数多少正常33周3天早产儿成活率多大怀孕三十三周，胎儿双顶径74，腹围246，股骨长61正常吗孕33周股骨长57怎么办？还能长吗33周胎儿只有4斤重，属于正常吗33周羊水指数多少正常33周羊水指数正常范围是8-1...