The measurement of cervical change is a fundamental part of tracking progress in late pregnancy and labor. Healthcare providers assess two primary measurements: effacement and dilation. These measurements indicate how the body is preparing the cervix for the passage of the baby. Understanding these terms helps demystify the numbers shared during prenatal appointments or early labor.
What Cervical Effacement Means
Cervical effacement is the process where the cervix softens, shortens, and thins out. Throughout pregnancy, the cervix is typically firm, long, and closed, with an average length of about 3 to 4 centimeters. As the body prepares for birth, uterine contractions and the pressure from the baby’s head help draw the cervix upward. This action effectively shortens the passageway, a process sometimes called cervical ripening, which allows the baby to enter the birth canal.
Interpreting the Percentage System
Effacement is tracked using a percentage scale ranging from 0% to 100%. A cervix that is 0% effaced is its normal, thick length, generally measuring 3 to 4 centimeters. Conversely, 100% effaced means the cervix has fully thinned out and is paper-thin.
A measurement of 60% effaced means the cervix has completed slightly more than half of its necessary thinning process. If the original length was approximately 4 centimeters, 60% effacement suggests the cervix has shortened to about 1.6 centimeters remaining. This percentage signifies measurable progress toward labor. While 60% is a positive indication of preparation, the timing of labor onset varies greatly and can still be days or weeks away.
Effacement Versus Dilation
Effacement and dilation describe two distinct changes happening in the cervix. Effacement is the thinning and shortening, measured in percentages (0% to 100%). Dilation is the opening of the cervix, measured in centimeters.
The cervix must open to 10 centimeters to be considered fully dilated, which is when the pushing phase of labor can begin. Both measurements are taken during a cervical check to give a complete picture of the body’s readiness. These two processes work in tandem, though first-time mothers often experience most of the effacement before significant dilation begins.
Progression Beyond 60 Percent
Reaching 60% effacement means the cervix is well into the early, or latent, phase of labor. For a vaginal delivery to occur, the cervix must ultimately reach 100% effacement and 10 centimeters of dilation. Once past the halfway mark, the rate of change often accelerates as contractions become stronger and more regular. The time it takes to progress from 60% to 100% effacement is highly variable, potentially taking hours to weeks. Individuals who have given birth before may progress more quickly through the remaining effacement and dilation.