What Is Effacement During Pregnancy: Symptoms, How To Measure

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Medically reviewed by Kimberly Langdon, MD

Cervical Effacement: Symptoms, How to Measure

There’s no way to tell exactly how close a pregnant woman is to giving birth. There are a few different ways to make a fairly accurate estimate of when a baby is going to be born, however, two being cervical effacement and dilation. 

What is Effacement During Pregnancy?

Cervical dilation and effacement are two ways a mother’s body clears the way for birth. The cervix is the connection between the vagina and uterus. Normally, it closes the way between the two, tightening shut. Before birth, it thins and opens so the baby can pass through. The thinning of the cervix is effacement and the opening is dilatation, more commonly called dilation.

Cervical Effacement and Dilatation

The Cervix

The cervix[1] is the tube connecting the uterus to the vagina. It’s made mostly of fibromuscular tissue and is generally about 3 or 4 centimeters long[2]. Most of the time, it’s closed to prevent passage from the uterus to the vagina. However, it has a canal that allow menstrual blood to pass into the vagina from the uterus.

Closing off the passage is the cervix’s primary job, but it does double duty, also producing cervical mucus. It can either encourage or discourage pregnancy, depending on the phase of the menstrual cycle. The cervix will also open slightly during menstruation to allow menstrual flow.

The part of the cervix that opens into the vagina, which might be seen during a gynecological exam, is called the ectocervix. The opening in the center is called the external os.

At the other end, opening into the uterus is the endocervix or endocervical canal. Between the ectocervix and the endocervix is an area called the transformation zone.

Cervical Dilatation and Effacement

As the first stage of labor begins, the normally tightly closed cervix thins and opens. It goes from about 3 centimeters wide (dilation) to just paper thin (effacement). The opening will go from basically closed, to ten centimeters wide. While that may seem like quite a change, it’s necessary for a baby’s head to pass through the birth canal. 

For some women, dilation and effacement may take several weeks during which the change happens gradually. On the other hand, dilation and effacement can happen more quickly. A quick transition is more likely with a first time mom.

Cervical effacement and dilation are triggered when you begin to feel contractions, at the very beginning of the first stage of labor. That prompts the baby to move down into the birth canal, in position to be born.

Symptoms of Cervical Effacement and Dilation

The symptoms of cervical effacement and dilation are really the first signs of starting labor[3]. We’re all familiar with some of those signs, although there are others that are harder to spot. Two signs of labor that are related to cervical effacement are:

  • Irregular contractions
  • A discharge from the vagina, either clear, pink, or bloody

The classic first sign is irregular contractions spaced fairly far apart. Those contractions are a signal to your cervix, among other things, to begin getting ready for the big day.

In the course of the pregnancy, the cervix will produce a mucus plug. It’s important as it closes off the passage between uterus and vagina until it’s time to give birth. As part of the preparations for that, the mucus plug has to go. 

It’s not as dramatic as your water breaking, when the amniotic sac opens. However, you may notice a discharge from the vagina that is either clear or a little bloody. The blood is normal, by the way, and not a sign of something wrong. This is sometimes called ‘show’ or ‘bloody show.’

The cervix will dilate at different rates for different pregnancies, so seeing a discharge may mean that birth is approaching quickly. It doesn’t necessarily mean that it’s happening right that moment, however. 

Contractions usually means that things are more urgent. That’s not always true, however. They may be Braxton Hicks contractions[4] rather than labor pains. Those are sort of like practice runs for the real thing and will fade away instead of growing stronger. A few signs you’re experiencing Braxton Hicks contractions include:

  • Not painful
  • Aren’t regular
  • Don’t last longer than 30 seconds
  • Don’t get closer together
  • May stop after changing positions

How to Measure Cervical Effacement and Dilation

Cervical effacement is measured in percentages and isn’t gauged precisely, instead being estimated by a doctor. A cervix that has not thinned at all is 0 percent effaced. One that is paper thin and wide enough for labor would be considered 100 percent effaced.

In some cases, the cervix effaces before it dilates. That happens commonly with first time moms. 

Dilation can be measured a little more precisely, from 0 to 10. The measurement roughly corresponds to centimeters, so that a cervix that is dilating to 5 would be opened about 5 centimeters. A woman’s cervix will usually dilate fully, to around 10 centimeters, before giving birth. 

Both effacement and dilation continue until the second stage, known as active labor, the first stage of the birthing process. At that point, the cervix goes from about 6 cm dilated to 10 cm. The cervix may already be 100 percent effaced at this point, or it may still need to thin further. When that process is complete, the baby is ready to come into the world.

The Stages of Labor and Birth

Giving birth isn’t usually very neat or tidy. To help keep things organized, doctors have divided the process of giving birth into three different stages[5]

First Stage of Labor

There’s a lot going on in a woman’s body as her due date gets closer. For most women, they’ll feel the labor contractions growing more powerful and increasing in frequency, until suddenly it’s clear that it’s time for a baby to be born. 

It can be hard to put a precise moment on when that happens, so the first stage of labor is said to ‘begin when labor starts[6].’ The threshold for that is when labor contractions are coming regularly, spaced between 3 and 5 minutes apart. 

The first stage is separated into two parts defined by the amount of cervical dilation. The first part is called the latent phase, during which the cervix dilates from 0 to 6 centimeters. In the second part, the active labor phase, the cervix completes dilating to 10 cm. At this point, the cervix is fully effaced and dilated.

Second Stage of Labor

The second stage begins when the cervix has completely dilated. The baby completes moving to the bottom of the uterus, usually head first. With the help of the mother, the baby is pushed out through the cervix in a vaginal delivery. In some situations, the baby is delivered by caesarean section instead. 

When the baby is born, the second stage of labor is complete. Many factors go into determining how long the second stage lasts. In general, newer mothers are more likely to have a longer labor. 

Third Stage of Labor

It may come as a surprise, but labor actually continues after the birth of the baby. The third stage begins after the birth of the baby and ends with the delivery of the placenta. This process can take as little as five minutes or take as long as a half hour. 

There is nothing more natural than giving birth. At the same time, it’s a complex process that a mom’s body has to adjust to accommodate. Most discussions focus on dilation, as that’s more directly important to the birthing process. However, cervical effacement is also an important part of preparing for birth.


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  1. https://www.facebook.com/WebMD (2012). Picture of the Cervix. [online] WebMD. Available at: https://www.webmd.com/women/picture-of-the-cervix#:~:text=The%20cervix%20is%20a%20cylinder,composed%20primarily%20of%20fibromuscular%20tissue.
  2. Radha Malapati, Vuong, Y.N. & Nguyen, T.M. (2013). Reporting cervical effacement as a percentage: How accurate is it? [online] ResearchGate. Available at: https://www.researchgate.net/publication/272878975_Reporting_cervical_effacement_as_a_percentage_How_accurate_is_it
  3. Mayo Clinic. (2019). Signs of labor: Know what to expect. [online] Available at: https://www.mayoclinic.org/healthy-lifestyle/labor-and-delivery/in-depth/signs-of-labor/art-20046184
  4. https://www.facebook.com/WebMD (2002). Braxton Hicks. [online] WebMD. Available at: https://www.webmd.com/baby/guide/true-false-labor#1
  5. Mayo Clinic. (2020). Stages of labor and birth: Baby, it’s time! [online] Available at: https://www.mayoclinic.org/healthy-lifestyle/labor-and-delivery/in-depth/stages-of-labor/art-20046545#:~:text=The%20first%20stage%20of%20labor%20and%20birth%20occurs%20when%20you,longest%20of%20the%20three%20stages.
  6. Hutchison J; Mahdy H; Hutchison J (2021). Stages of Labor. [online] . Available at: https://pubmed.ncbi.nlm.nih.gov/31335010/

Medically reviewed by:

Sean Newton has nearly ten years of experience as a health and fitness writer, focusing on diet and its effects on your health. He also is an avid athlete and martial artist, specializing in bodyweight exercises and movement training. Together with an evidence-based approach to good health, his goal is to lay out the facts for readers, so they can make informed choices.

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