A woman's cervix needs to be 100 percent effaced and 10 centimeters dilated to give birth vaginally; therefore, being 70 percent effaced means her cervix is 30 percent away from being ready for childbirth. Being two centimeters dilated means her cervix needs to dilate 8 more centimeters. According to American Pregnancy, effacement refers to how much the cervix thins out or "ripens" in preparation for birth. Cervical dilation refers to the opening of the cervix.
According to Just Mommies, towards the end of the 40-week span that is human pregnancy, a woman's body begins to prepare for childbirth. The doctor or midwife is able to tell how close a woman is to delivering based on how effaced and dilated her cervix is. Prior to delivery and when a woman is not pregnant, the cervix is long and thick. As the time for delivery approaches, the cervix starts to shorten and thin out. Essentially, it pulls up and almost becomes one with the lower uterus. When the cervix is completely thinned or ripened, vaginal childbirth is imminent. As the cervix starts to thin and ripen, it also starts to open up. The cervix must open to allow a child's head through the birth canal. According to What to Expert, it is not uncommon for women to have some sort of dilation for weeks prior to delivery, but the cervix must be a full 10 centimeters dilated to be ready for delivery.