A cervical exam tells your doctor or midwife a few things about your cervix. However, the number most pregnant women focus on is how open, or dilated, the cervix is. Sometimes it can be confusing to know exactly what this number really does (or doesn’t) mean. Here are some tips to help make sense of it all.
1. A closed cervix means you are not dilated at all. This means your doctor or midwife can’t pass a finger through your cervical os, or cervical opening. Most first-time moms will have a closed cervix for the majority of their pregnancy.
2. A fully dilated cervix is 10 centimeters open. This is about the size of a bagel, and means that when your cervix is measured with two fingers, they can be stretched 10 centimeters across. Other terms to say you are 10 centimeters dilated are that you are fully or completely dilated. Time to push and have a baby!
3. Women who’ve given birth before may have a cervix that remains open a little. For some women, the cervix never really goes back to being closed. Therefore, it can be normal in subsequent pregnancies to be a few centimeters dilated the whole time without this being a sign of preterm or real labor.
4. There is no magic amount of opening that means you are in labor. A single measurement is usually not that useful in figuring out whether you are in labor. What this means is some women walk around for weeks being 4 centimeters dilated, while others are that same measurement and in active labor. It’s all about taking into account the whole picture: the rest of the cervical exam, how frequently contractions are happening, and if a repeat exam a few hours later shows any change.
5. Active labor happens at different dilations for different women. We used to say that once a woman was 4 centimeters dilated that she was in active labor and she was going to have her baby soon. Now we know that some women aren’t in true active labor until up to 6 centimeters! Why is this important? If you are being told you need a C-section at 4 centimeters dilation because your labor is “stuck” it may be that you are not really in labor at all yet. Giving women more time to dilate and realizing this can help us avoid unnecessary C-sections.
6. How fast you dilate in labor depends on a few things. In general, women who’ve had a baby before will dilate faster than first-time moms. Epidurals can slow down the rate of dilation some, but they don’t increase your risk of a C-section. A general rule of thumb is that once you are in active labor, the cervix will dilate about 1 to 1.5 centimeters an hour, but it can certainly vary.
7. You shouldn’t push until your cervix is completely dilated. This is because pushing before your cervix completely opens can cause swelling on the cervix that can make a vaginal delivery more difficult. Again, exceptions exist: women who’ve given birth before can sometimes push sooner than this and have no problems, as can women who are delivering a smaller preterm baby.
Reviewed by Dr. Jen Lincoln, April 2020
- A closed cervix is not open at all, while a fully dilated cervix is 10 centimeters open.
- Women who’ve given birth before can be dilated some in their next pregnancy and not be in labor.
- There is no magic number to mean you are in labor.
- Active labor happens at different dilations for different women.