Cervical changes in labor
The cervix is the gateway to the baby. During pregnancy, a plug covering the cervix works like a cork holding the umbilical sac and fetus in place in the uterus. As labor approaches, hormonal changes cause the plug to release starting the beginning stages of labor. Cervical changes can take place over weeks.
The mucus plug
Most women correlate the loss of the cervical or mucus plug as the beginning of labor, but this is not always the case. As the cervix thins and opens, the plug may come loose and fall into your undergarments, wipe off on toilet paper or fall into the toilet. You can lose your cervical plug in the shower while walking or sleeping, but the plug can fall out weeks before active labor begins. Some women never experience active labor even though they have lost the mucus plug.
Prior to the latter weeks of pregnancy, the cervix typically measures about four centimeters long. As you approach the final weeks of pregnancy, the cervix starts to efface or shorten. Effacement progress is measured in percentages. The most common terminology is 25%, 50%, 75% and 100% or three centimeters, two centimeters, one centimeter and completely effaced, respectively. When you are 100% effaced, your cervix is thinned out and ready for delivery.
Not only does the cervix thin out or shorten it also opens up or dilates. Dilation is measured on a 10-centimeter scale. The first changes in dilation are slow. Pregnant women can dilate up to three centimeters at home and stay at that dilation for several weeks with no further indication of labor. When active labor begins, dilation typically speeds up.
Effacement and dilation – partners in labor
Doctors will physically examine the cervix for effacement and dilation via palpation. This means your doctor will feel the cervix via a pelvic exam in the office or hospital to judge just how close you are to delivery. When you are 100% effaced and completely dilated you are ready to give birth. If labor is taking too long, there is a threat to the health of the baby if unprogressive labor continues or another health issue requires attention; your doctor may attempt to speed up effacement and dilation by breaking your bag of water or adding a medication to your IV.
The stages of cervical changes
There are four stages of cervical dilation. The latent phase is when your cervix is between zero and ten centimeters dilated. The active labor stage starts at four centimeters and runs through seven centimeters dilation. When you reach eight centimeters you are in the transition stage of cervical dilation and by the time you reach 10 centimeters your cervix is complete.
Prostaglandins are partially responsible for cervical dilation. Your body naturally produces prostaglandins, but your doctor can use a synthetic form applied to the cervix to speed up the process. Contractions, even Braxton Hicks contractions, also play a crucial role in thinning and dilating the cervix.
Labor and Delivery Guide