Cervical dilation is the measurement of how open the cervix, the lower part of the uterus, has become in preparation for childbirth. This measurement is a primary indicator used by healthcare providers to monitor the progress of labor. A cervical check, typically performed as a manual exam, assesses not only dilation but also effacement, which is the thinning of the cervix. Understanding when these checks occur is important, as they are a standard part of late pregnancy care and labor management, providing information that guides medical decisions.
Routine Checks Before Labor Starts
Healthcare providers often offer cervical checks during routine prenatal appointments starting around 36 to 40 weeks of gestation. These exams are generally considered optional unless a specific medical condition warrants them. The purpose of these checks is to establish a baseline status of the cervix before labor begins spontaneously. Providers assess how many centimeters the cervix is dilated, how much it has effaced or thinned out, and the position of the baby’s head within the pelvis.
The results of these pre-labor checks do not reliably predict the exact day labor will start. A person can walk around for weeks with a cervix that is several centimeters dilated, or they may have a completely closed cervix one day and deliver within hours. However, this information can be useful for planning purposes, especially if an induction is being considered, as the cervical status is a component of the Bishop score used to gauge the likelihood of a successful induction. They carry a small risk of introducing bacteria, which is why they are not performed earlier in pregnancy.
Initial Assessment When Labor Begins
The first cervical dilation check in a hospital or birthing center setting is a critical step for triage and admission once labor is suspected. This assessment is typically performed when a person arrives reporting regular, painful contractions, or if their membranes have ruptured. The primary goal of this initial check is to determine if the person is in the active phase of labor, which is generally defined as having a cervix dilated to 6 centimeters or more.
If the dilation is less than 6 centimeters, the labor is often considered latent, and the patient may be sent home to continue laboring in comfort or monitored for a period before a final decision is made. This initial measurement is essential because hospital admission during the early or latent phase of labor may be associated with an increased likelihood of interventions, like Pitocin use or epidurals.
Monitoring Dilation During Active Labor
Once a patient is admitted and confirmed to be in active labor, subsequent dilation checks become a routine part of monitoring progress. The frequency of these checks typically occurs every two to four hours. The exact timing can be influenced by specific events, such as a request for pain medication, a significant change in the contraction pattern, or concerns about the baby’s heart rate.
A lack of expected progress, often termed “failure to progress,” is determined when the cervix is not dilating at a sufficient rate in the active phase, which may prompt a discussion about interventions. The measurements continue until the cervix reaches full dilation at 10 centimeters, signifying that the opening is wide enough for the baby’s head to pass through and that the pushing stage can safely begin.
Medical Reasons to Limit Dilation Checks
In certain medical situations, healthcare providers will intentionally limit or completely avoid performing cervical dilation checks due to specific safety risks. A primary reason is the presence of placenta previa, a condition where the placenta covers all or part of the cervical opening. Inserting fingers into the cervix in this situation could disrupt the placental tissue, leading to severe hemorrhage. In such cases, an ultrasound is used to confirm the placental location, and digital exams are avoided throughout the pregnancy and labor.
Another significant contraindication is the presence of active genital herpes lesions at the time of labor. A cervical check could increase the risk of the baby contracting the virus as it passes through the birth canal, which can lead to severe neonatal infection. Once the amniotic sac has ruptured, particularly in cases of Preterm Premature Rupture of Membranes (PPROM), the number of cervical exams is minimized. This is because each exam increases the potential for introducing bacteria from the vagina into the uterus, raising the risk of an intrauterine infection, a condition known as chorioamnionitis.