Cervical dilation is the opening of the cervix, the firm, lower part of the uterus that connects to the vagina. This process is a fundamental sign that the body is preparing for childbirth, as the cervix must widen to create a passage for the baby. The measurement of this opening is the primary indicator medical professionals use to track the progression of the first stage of labor. Without sufficient dilation, the baby cannot move from the uterus into the birth canal for delivery.
Understanding Full Cervical Dilation
A cervix that is closed is considered zero centimeters (0 cm) dilated, and a measurement of ten centimeters (10 cm) signifies full dilation, often referred to as “complete.” Reaching this 10 cm diameter is required before the second stage of labor, which involves pushing the baby out, can begin. This specific measurement is the approximate diameter needed to allow the average full-term baby’s head to pass safely through the pelvis and into the vagina.
During labor, a medical professional uses a digital examination to determine the extent of dilation. This involves inserting two gloved fingers into the vagina to manually feel the opening of the cervix. The professional then estimates the width of the opening between the fingertips to approximate the measurement in centimeters. The first stage of labor is categorized into phases based on this scale, moving from the latent phase (0–6 cm) to the active phase (6–10 cm).
Why Fingers Are Not a Standard Measurement
While a provider uses their fingers to estimate the opening, the actual number of fingers that fit is inconsistent and highly subjective. The width of an individual’s fingers varies significantly between one medical professional and the next, leading to potential inaccuracies in measurement. It is possible for one practitioner to measure 7 cm while another might measure 8 cm on the same patient at the same time.
For the average person to visualize a 10 cm opening, it is more helpful to use common objects as a reference. A fully dilated cervix is roughly the diameter of a small grapefruit, a standard bagel, or the top of a large can of wipes. At 10 cm, the cervical tissue has essentially been pulled back, leaving a large, open passage. While it might accommodate five or more fingers pressed together, relying on this finger count is imprecise and can misrepresent the true progression of labor.
What Happens Once Dilation is Complete
Reaching 10 cm dilation signals the end of the first stage of labor and the beginning of the second stage, the delivery phase. However, dilation alone is not the only factor needed for a safe delivery. The cervix must also achieve 100% effacement, which is the process of thinning and shortening from its normal, thicker state. Full effacement, often described as “paper-thin,” must coincide with full dilation for the baby to pass through the birth canal effectively. Once both 10 cm dilation and 100% effacement are confirmed, the mother typically begins the active pushing phase, during which the baby’s position and station are also tracked.