宫颈短，是宫颈松弛扩张的前奏，不及时埋箍，就会发展到宫口松开，胎膜早破，难免流产。Cervix is short, it is the prelude of cervical flabby dilate, do not bury in time hoop, can develop to palace mouth loosen, fetal membrane is broken early, hard to avoid miscarriage.