The late third trimester often brings questions about the body’s readiness for labor. As the final weeks approach, many healthcare providers begin offering internal examinations to check the cervix, often starting around 36 weeks. Changes in the cervix are a key indicator of the body preparing for delivery. Understanding these measurements can help manage expectations during this waiting period.
Understanding Cervical Dilation and Effacement
Two distinct physical changes in the cervix are measured during a late-term examination to assess readiness for labor. Dilation refers to the opening or widening of the cervix. This measurement is given in centimeters, progressing from zero to the full 10 centimeters needed for a vaginal birth.
The second measurement is effacement, which describes the thinning and shortening of the cervix. Throughout most of pregnancy, the cervix is long and firm, but it gradually softens and thins out as the body prepares for labor. Effacement is measured as a percentage, where zero percent means the cervix is thick and 100 percent means it is completely thinned out.
These two processes can happen simultaneously, but they often follow different patterns. Individuals giving birth for the first time usually experience significant effacement before they begin to dilate. Those who have previously given birth may find that their cervix dilates slightly before full effacement occurs. Both 100 percent effacement and 10 centimeters of dilation are necessary before the final pushing stage can begin.
Dilation Status at the 36-Week Appointment
Cervical checks are commonly initiated around the 36-week mark, even though the full-term period generally starts at 37 weeks. Finding some degree of cervical change at this appointment is a normal physiological occurrence. A healthcare provider may find the cervix is dilated anywhere from one to three centimeters.
This finding is especially common in individuals who have had a baby before, as their cervix may retain some dilation from previous deliveries. Conversely, having a closed, uneffaced cervix at 36 weeks is also considered normal, particularly for first-time parents. The presence or absence of early dilation reflects the wide variability in how bodies prepare for childbirth. These changes are considered part of the cervix’s natural “ripening” process in the weeks leading up to labor.
When Dilation Does Not Mean Immediate Labor
While dilation is a necessary step for labor, finding the cervix open at 36 weeks is a poor predictor of when labor will actually begin. Many individuals can be one to three centimeters dilated for several weeks before contractions start. This phenomenon of “walking around dilated” is common and does not indicate that delivery is imminent.
Research suggests that even advanced cervical dilation, such as three centimeters or more between 32 and 36 weeks, does not reliably indicate true labor is underway. One study showed that most patients with contractions and advanced dilation in this timeframe remained pregnant for more than a week without intervention. The body may simply be preparing gradually without an immediate timeline for active labor. Healthcare providers monitor for other signs, such as consistent, painful contractions or changes in fetal status, as dilation alone is not enough to signal the start of the delivery process.