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.

How long can you be effaced before labor?

Some women may reach 100% effacement within a few hours. For others, cervical effacement may occur slowly over several weeks. The same applies to dilation. It is not uncommon for a woman to be 1–2 cm dilated a couple of weeks before going into labor.

Can you be 100 effaced and not dilated?

Both effacement and dilation are the result of your uterus contracting. While there's no average time it takes to progress from 0 to 100 percent, you can't fully dilate to 10 centimeters until you're fully effaced.