Effacement is measured in percentages. Once you hit 100 percent effaced, your cervix has thinned out enough for childbirth. So, if your obstetrician tells you you’re “70 effaced” or “70 percent effaced,” it means you’re about three–quarters of the way to being ready for delivery.

Once your cervix reaches 80 percent effacement, it’s almost short enough to allow your baby through the uterus, assuming it is accompanied by dilation. You may reach 80 percent effacement or higher during the early stage of labor, or this may happen once you reach active labor.