To reach a stage in labor when a large segment of the fetal scalp is visible at the vaginal orifice.Used of a fetus or the head of a fetus.是什么意思_To reach a stage in labor when a large segment of the fetal scalp is visible at the vaginal orifice.Used of a fetus or the head of a fetus.在线翻译_英语_读音_用法_例句