Cervix effacement refers not to the way the cervix, the neck of the uterus, opens (dilation), but the process by which it thins and shortens. To visualize the process, imagine donning a turtleneck sweater. As labor progresses, the cervix thins out, just like the turtleneck as the pressure of a person's head pushes against the opening. It thins and stretches to allow the head to pass through the opening. When the cervix is fully thinned, it resembles the turtleneck just before a person's head comes through. The fabric is taut, pulled thin and shortened from its dimensions when at rest.
After cervical effacement is complete, the baby will soon arrive. The degree of cervix effacement is a better predictor of a quick or close labor than dilation. This process can take much longer than dilation itself, so the higher the percentage of effacement that occurs in advance of active labor, the faster the baby will arrive.
Effacement in pregnancy is measured on a percentage basis from 0 to 100 with 0% meaning no thinning and 100% considered complete. At 0%, the cervix is approximately 2 inches long and is thick and hard. At 100%, the cervix is paper-thin to allow the baby's head can easily slip through the opening.
Page Last Modified by Catherine Beier, MS, CBE
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