第一产程潜伏期是指从

A.不规律宫缩到宫口开大3cm

B.规律宫缩到宫口开大3cm

C.不规律宫缩到宫口开大2cm

D.规律宫缩到宫口开大2cm

E.规律宫缩到宫口开大5cm