A cervical exam is a manual check performed by a healthcare provider to assess the readiness of the cervix for childbirth. The primary measurement is dilation, which refers to the opening of the cervix, the muscular ring at the base of the uterus. Dilation is measured in centimeters (cm), starting at zero and progressing to ten centimeters, which is considered full dilation. Reaching ten centimeters indicates the second stage of labor can begin.
Routine Checks in Late Pregnancy
Obstetricians and other maternity care providers begin offering cervical exams for dilation in the final weeks of pregnancy, usually starting between 36 and 37 weeks of gestation. These checks are routine and are performed during weekly prenatal appointments leading up to the estimated due date. The purpose of these early checks is to establish a baseline for any cervical change that may have begun before labor starts.
Knowing a patient’s starting point can be helpful if they require a medical induction, as a partially dilated or thinned cervix suggests a higher likelihood of success. These exams often coincide with the screening test for Group B Streptococcus (GBS), a common bacterium requiring antibiotic treatment during labor if the test is positive. However, a cervical exam in late pregnancy is not a reliable predictor of when labor will begin.
A patient could be several centimeters dilated for weeks without going into labor, while another may have a completely closed cervix until active labor starts. These routine checks provide a snapshot of the current state of the cervix but do not forecast the timing of delivery. Since they do not change the immediate care plan for a healthy pregnancy, these checks are optional for the patient.
Dilation Checks During Active Labor
Once a patient is admitted in active labor, the purpose and frequency of cervical checks shift from routine assessment to monitoring progression. The goal is tracking the patient’s advancement toward ten centimeters of full dilation. During the first stage of labor, these examinations are offered every two to four hours to determine if the cervix is opening steadily.
A cervical exam is also performed when a patient feels a strong urge to push, confirming complete dilation before the pushing stage begins. Checks may be required more frequently following the rupture of membranes or before administering pain medications like an epidural. In these cases, the provider confirms the stage of labor or rules out complications like umbilical cord prolapse.
The provider uses dilation to gauge the effectiveness of contractions and ensure the labor pattern is progressing within clinical guidelines. If labor stalls or slows significantly, the measurement helps the provider make decisions about potential interventions. Monitoring this progression is essential for managing labor toward delivery.
Understanding Effacement and Station
While dilation measures the cervix’s opening, the cervical exam also assesses effacement and station. Effacement refers to the thinning and shortening of the cervix, which must occur before the baby can pass through the birth canal. It is measured in percentages, where 0% effacement means the cervix is long and thick, and 100% means it is completely thinned out.
The cervix must be 100% effaced for the second stage of labor to begin, even if full dilation has been reached. Effacement often begins before dilation, particularly in first-time mothers, as the body gradually prepares the cervical tissue. This measurement helps determine a patient’s readiness for pushing.
Station describes the position of the baby’s head in relation to the mother’s pelvis, measured against the bony points known as the ischial spines. This measurement is expressed as a number ranging from -5 to +5. A zero station means the baby’s head is level with the ischial spines and is considered “engaged” in the pelvis.
Negative numbers indicate the baby’s head is higher in the pelvis, while positive numbers mean the head has descended lower into the birth canal. A station of +3 or higher suggests the baby’s head is nearing the vaginal opening, which is an important sign for the final stages of labor. Tracking the station helps the provider understand how well the baby is moving down through the pelvis.
Patient Autonomy Regarding Cervical Exams
The decision to undergo a cervical exam, both during routine late-pregnancy checks and during labor, rests with the patient under the principle of informed consent. Patients have the right to consent to or refuse any medical procedure, including these physical assessments. Routine checks before labor are optional, and declining them will not affect the management of an otherwise healthy pregnancy.
During active labor, while providers rely on this information to monitor progression, patients can still request less frequent checks or refuse them. Patients should discuss their preferences for cervical exams with their care team beforehand, as the checks can be uncomfortable or disruptive to labor rhythm. A refusal can only be overridden in rare situations when the information is medically necessary to prevent immediate harm to the mother or baby.
For example, a provider may recommend a check if there is sudden fetal distress or heavy bleeding to rule out an emergency. In all other circumstances, the patient must be fully informed of the reasons for the exam and understand their right to decline. Open communication with the care team ensures that the patient’s bodily autonomy is respected throughout the birthing process.