The final weeks of pregnancy involve intense anticipation, often marked by routine prenatal checks that measure the body’s readiness for birth. Receiving a report about cervical changes or fetal descent can spark both excitement and confusion. These findings are snapshots of a dynamic biological process, offering clues about progression without providing a firm timeline for the start of labor. Understanding the context of these measurements helps manage the final waiting period with accurate information.
The Three Key Measurements of a Cervical Check
A cervical check is a physical assessment that provides three distinct measurements to evaluate the body’s progress toward labor. These three components—dilation, effacement, and station—work together to paint a comprehensive picture of the cervix and the baby’s position. The process involves a manual examination where the provider uses their fingers to assess internal changes.
Dilation refers to the opening of the cervix, the muscular neck of the uterus. This measurement is expressed in centimeters, progressing from closed (0 cm) to fully open (10 cm). Full dilation (10 cm) is necessary for the baby to pass through the birth canal and is roughly the diameter of a newborn’s head. Since the measurement is done manually, it can be somewhat subjective.
Effacement describes the thinning, softening, and shortening of the cervix, measured in a percentage from 0% to 100%. Before labor, the cervix is typically long and firm, but it must become 100% effaced before the baby can descend easily. For first-time parents, effacement often happens before significant dilation begins. Those who have given birth before may experience both effacement and dilation simultaneously.
Station indicates how far the baby’s head has dropped into the pelvis, known as fetal engagement. This is measured in relation to the ischial spines, which are bony protrusions inside the pelvis. The measurement uses a scale, typically ranging from -5 to +5. A 0 station means the baby’s head is level with the ischial spines and is considered engaged. A negative number means the head is above the spines, and a positive number means it has descended below them.
Interpreting 1 cm Dilation and Fetal Engagement
Finding 1 cm dilation means the cervix has started to open, but this status alone is not a reliable predictor of when labor will begin. For many people, especially those who have given birth before, the cervix may remain at 1 cm for days or even weeks. This stage is considered part of the early or latent phase of labor, which involves mild, often irregular contractions that soften and open the cervix.
The latent phase typically progresses from 0 cm up to about 4 to 6 cm of dilation and is frequently the longest stage of the process. Because a small degree of dilation can persist for an extended time, 1 cm indicates preparation for childbirth, but not that birth is imminent. The ability to “feel the baby’s head” is a sign of favorable fetal engagement, meaning the baby has moved down into the pelvis.
When the widest part of the baby’s head has passed into the pelvic brim, the baby is considered engaged, often corresponding to a station of 0 or a low negative number. This descent, sometimes called “lightening,” is a positive sign of readiness, especially for first pregnancies, and suggests the baby is well-positioned for birth. While engagement is necessary, the cervix must still continue to thin and open to 10 cm for delivery.
Recognizing Active Labor and When to Go to the Hospital
The shift from latent labor to active labor is marked by a noticeable change in the frequency, intensity, and regularity of contractions. Active labor is generally defined as the point when the cervix has dilated to about 6 cm and contractions become much stronger. Contractions during this phase are strong enough to require focus and may prevent talking.
The progression to active labor is often the point at which healthcare providers advise heading to the hospital or birthing center. A common guideline is the “5-1-1 rule”: contractions occur every five minutes, last for one full minute, and maintain this pattern for at least one hour. This consistent pattern indicates that the uterine muscles are working rhythmically and effectively to open the cervix.
Other physical signs signal a need to contact a provider or go to the hospital. These include the rupture of membranes, commonly known as the “water breaking,” which can be a sudden gush or a slow trickle. A noticeable “bloody show,” which is pinkish or brownish mucus discharge, suggests the cervix is changing, especially when combined with regular contractions. Heavy vaginal bleeding, severe pain without relief between contractions, or a significant decrease in the baby’s movements are reasons to seek medical attention immediately.