Cervical dilation is the primary physical measurement used by healthcare providers to track the progression of labor and determine when delivery is imminent. This process involves the cervix, the lower, narrow part of the uterus, opening up to allow the baby to pass through the birth canal. Accurately measuring this change requires training and precision.
Defining Dilation and Effacement
Cervical change during labor involves two distinct but related processes: dilation and effacement. Dilation refers to the opening of the cervix, measured in centimeters, starting at zero and progressing to ten centimeters. Ten centimeters signifies full dilation, which is required for a vaginal delivery. Effacement describes the thinning and shortening of the cervix, measured in percentages from zero to one hundred percent. Both full dilation and full effacement must be achieved before the pushing stage of labor can begin.
The Standard Professional Cervical Exam
A healthcare provider, such as a doctor or midwife, performs a cervical exam to manually assess the progress of labor. This procedure, also known as a sterile vaginal exam, involves the provider inserting one or two gloved, lubricated fingers into the vagina to reach the cervix. The provider then estimates the diameter of the cervical opening to determine the dilation measurement in centimeters.
During the same examination, the provider also assesses effacement by feeling the thickness of the cervix and determining its percentage of thinning. They will also note the position of the baby’s head in relation to the mother’s pelvis, which is called the station. These exams are typically performed upon admission, periodically during active labor, and when there is a change in symptoms or concern about progress.
The use of sterile gloves and technique is important to minimize the risk of introducing bacteria into the uterus, especially if the amniotic membranes have already ruptured. This technique provides objective data to guide care decisions and manage the labor process safely.
Safety Considerations and Monitoring Progression at Home
Attempting to perform a cervical check on oneself at home is strongly advised against by medical professionals due to significant risks and potential for inaccuracy. Self-examination can easily introduce bacteria into the vagina, posing a serious risk of infection to both the parent and the baby. This risk is especially high if the amniotic sac, or “water,” has already broken, creating a direct pathway for infection into the uterus. Assessing dilation and effacement accurately requires significant training and practice, meaning a self-check is likely to yield misleading information.
Instead of internal checks, individuals should focus on monitoring external signs of labor progression. The most reliable method is timing contractions, noting their frequency, duration, and intensity. True labor contractions will consistently become longer, stronger, and closer together, unlike the irregular pattern of Braxton Hicks contractions.
Tracking the expulsion of the mucus plug, often referred to as the “bloody show,” also suggests cervical change is occurring. Monitoring for the rupture of membranes, or the “water breaking,” is another important sign that requires immediate contact with a healthcare provider.
What Your Dilation Number Means
The dilation number reported by a healthcare provider is used to define the stage of labor and predict further progress. The first stage of labor, which involves all cervical change, is classically divided into three phases.
The latent phase is the longest and least intense part of labor, spanning from zero to about three or four centimeters of dilation. Once dilation reaches four to six centimeters, labor typically enters the active phase, where cervical change accelerates and contractions become noticeably stronger and more regular. This active phase continues until the cervix is dilated to about eight centimeters.
The final phase, known as transition, covers the progression from eight to the final ten centimeters of dilation. Full dilation at ten centimeters signifies the end of the first stage of labor and the beginning of the second stage, when pushing commences.
A widely used guideline for knowing when to head to the hospital is the “5-1-1 rule.” This advises contacting a provider when contractions are five minutes apart, last for one full minute, and have followed this pattern for at least one hour. This guideline, along with the rupture of membranes or sudden heavy bleeding, indicates it is time to seek professional care.