Effacement: What Effaced Means, the Percent Scale and How It Differs From Dilation

Effacement is the thinning and shortening of the cervix before and during labor, reported from 0 percent (long and thick) to 100 percent effaced (completely thinned out).

If your provider just said something like “2 centimeters and 50 percent,” you got two measurements in one breath. The centimeters are dilation. The percent is effacement, and it gets far less explanation.

This guide explains what effaced means, how to read the percent scale, how effacement differs from dilation and station, and what it can and cannot tell you about when labor will start.

What Does Effaced Mean?

The cervix is the lower part of the uterus. During pregnancy it stays long, firm and closed, which Cleveland Clinic compares to a cork in a bottleneck: it keeps your baby in and germs out.

Sources give slightly different starting lengths. Cleveland Clinic says the cervix is 3 to 4 centimeters long during pregnancy, Mayo Clinic says 3.5 to 4 centimeters before labor, and StatPearls, a National Institutes of Health (NIH) clinical reference, says an uneffaced cervix is typically about 4 centimeters. Once it is fully effaced, Cleveland Clinic describes it as thin as a piece of paper.

When does it start? Mayo Clinic says the cervix starts to soften, shorten and thin as early labor begins. Cleveland Clinic explains the trigger: as delivery nears, your baby drops into the pelvis and, if head-down, presses on the cervix. Labor contractions add more pressure.

The Effacement Percent Scale: 0, 50, 80 and 100 Percent Effaced

What does 50 effaced mean? If your provider says you are 50% effaced (often typed as “50 effaced”), your cervix has thinned to roughly half its usual length. It is the midpoint of thinning, not the midpoint of labor, and not a countdown.

What does 100 effaced mean? Your cervix is fully thinned. That is one of two finish lines: Cleveland Clinic says the cervix must be 100% effaced and 10 centimeters dilated before the pushing stage of a vaginal delivery can begin.

Why the number is an estimate. StatPearls explains that effacement is assessed by estimating how much cervical length remains compared with an uneffaced cervix, and it calls the exam-based Bishop score, which includes effacement, a subjective assessment. Two examiners may not report exactly the same percent.

Effacement vs Dilation vs Station

Cleveland Clinic explains that effacement affects the entire cervix, while dilation affects the part that opens into the vagina. The two go hand in hand, and both happen because of uterine contractions.

You may hear all three as a string of numbers. “3 centimeters, 70 percent, minus 1” means 3 centimeters dilated, 70% effaced, and the baby’s head about 1 centimeter above the ischial spines.

Mayo Clinic notes that cervical changes can be very slow at first and speed up in active labor, when the cervix is open 6 centimeters or more. We cover the phases in early labor vs active labor.

How Your Cervix Is Checked (and Why You Cannot Reliably Check It Yourself)

Effacement is found on a cervical exam done by a clinician, toward the end of pregnancy and during labor. StatPearls describes the technique: the examiner locates the opening of the cervix with two fingers, estimates the distance between them (dilation), and estimates how much of the cervix’s length remains (effacement).

• During labor: StatPearls says labor progress is typically monitored with cervical exams every 2 to 4 hours, unless there is a reason to check more often.
• Possible preterm labor: March of Dimes says your provider may do a pelvic exam or a transvaginal ultrasound to see whether your cervix has started to become thinner and open.

Can you check your own effacement? Not reliably. Cleveland Clinic says trying to check yourself can be hard when you do not have training to do cervical checks. A self-check cannot give you a number to trust.

There is also a safety reason. StatPearls notes that frequent cervical exams carry a higher risk of infection, particularly after the membranes have ruptured (after your water breaks). If you want to know your numbers, ask at your next visit.

Can You Feel Your Cervix Thinning?

Cleveland Clinic is direct: you cannot feel your cervix effacing. You may suspect it is changing because of other late pregnancy signs: losing your mucus plug, feeling your baby drop, pelvic pressure and more vaginal discharge.

Mayo Clinic says the baby settling deep into the pelvis, called lightening or engagement, can happen anywhere from a few weeks to a few hours before labor begins. For other late pregnancy changes, see pregnant belly by month and when nesting starts.

Do Braxton Hicks cause effacement? Cleveland Clinic says Braxton Hicks contractions will not make your cervix change or efface, and MedlinePlus (NIH) says they do not result in the cervical changes that suggest true labor. True labor contractions come regularly, get closer together and get stronger over time (MedlinePlus). Our guides to what contractions feel like and prodromal labor go deeper.

First Baby vs Later Pregnancies

The order of events often differs by pregnancy. Cleveland Clinic describes three patterns:

• First delivery: chances are, your cervix will efface before it dilates. You can be effaced but not dilated.
• Second or third pregnancies: your cervix can be dilated and not effaced. Cleveland Clinic says this is more common in later pregnancies.
• Either: in some cases, the cervix effaces and dilates at the same rate.

In labor, effacement can also be slow. Cleveland Clinic lists possible reasons, including weak contractions and a baby who is breech or large.

Does Being Effaced Predict When Labor Will Start?

No. Cleveland Clinic says there is no way to know how long effacement will take. Once it starts, you are close to labor or in it, but no one can know exactly how close. It gives two extremes: some women are 2 centimeters dilated and 30% effaced for weeks, and others remain 0% effaced and 0 centimeters dilated until a few days before delivery.

• What a cervical check can tell you: where your cervix is today, and whether it has changed since the last exam. Mayo Clinic notes that no one knows for sure what triggers labor.
• What it cannot tell you: the day labor will start, or how long labor will last.

So “still 0%” at a late visit is not a prediction that you will go past your due date, and 80% is not a promise that tonight is the night. For signs that things are moving, see signs that labor is 24 to 48 hours away and our third trimester guide.

The Mucus Plug and Bloody Show

The mucus plug is a thick piece of mucus that blocks the opening of the cervix during pregnancy and helps keep bacteria out of the uterus (Cleveland Clinic). As the cervix begins to efface and dilate, the plug can come out.

• What it looks like: Cleveland Clinic describes it as clear, off-white or slightly bloody (red, brown or pink), stringy, sticky and jelly-like, about 1 to 2 inches long and 1 to 2 tablespoons in volume.
• When: most women do not lose it until after 37 weeks of pregnancy.
• What it means: losing it generally means your cervix has started to dilate, efface or both. Labor may follow within hours or days, or not for a few weeks.
• Bloody show: MedlinePlus says bloody or brownish discharge may mean your cervix has begun to dilate.

Amount matters. Mayo Clinic says vaginal bleeding as heavy as a typical menstrual period means contacting your healthcare team right away. Watery fluid is a different sign: see signs of leaking amniotic fluid.

The Bishop Score and Cervical Ripening Before an Induction

If an induction is being planned, effacement becomes part of a score. StatPearls describes the Bishop score, introduced by Edward Bishop in 1964, as a cervical assessment system used to predict the success of labor induction. It has five parts: dilation, effacement, the baby’s station, and the position and consistency of the cervix. Effacement is scored from 0 to 3 points, and the total runs from 0 to 13.

On the traditional scale, StatPearls describes a score of more than 8 as a favorable cervix, and says the score helps determine whether cervical ripening is needed first.

Cervical ripening is how a care team prepares a cervix that is not ready. StatPearls lists two approaches: medicines (prostaglandins, most commonly misoprostol and dinoprostone) and mechanical methods. Your team chooses based on your history.

Can you speed up effacement at home? Every ripening method in the sources we reviewed is a medical one, done by a care team. Talk with your provider before trying anything meant to “ripen” your cervix.

A Thinning Cervix Before 37 Weeks: Short Cervix and Preterm Labor

Before 37 weeks, a thinning or shortening cervix is a medical issue. Cleveland Clinic says the cervix can sometimes efface too soon, which can cause you to go into labor early. The causes it lists are cervical insufficiency, a shortened cervix, injury to the cervix and prior surgery on the cervix.

• Cervical insufficiency: StatPearls defines it as the cervix painlessly dilating during the second or early third trimester, and says it complicates up to 1% of pregnancies. It causes no symptoms or only mild ones: pelvic pressure, backache, more vaginal discharge or spotting.
• Short cervix: StatPearls says a shortened cervix is typically defined as a cervical length of less than 25 millimeters on screening ultrasounds, which are typically transvaginal scans done between 16 and 24 weeks for people with a prior preterm birth.
• Treatment: StatPearls describes vaginal progesterone and cerclage, a stitch placed around the cervix. Which one fits is your obstetric provider’s decision.

March of Dimes defines preterm labor as labor that happens before 37 weeks of pregnancy, and says to call your health care provider right away if you have even one sign of it. The signs are listed below.

Related Betteroo Guides

• Early labor vs. active labor
• What do contractions feel like?
• Signs that labor is 24 to 48 hours away
• Prodromal labor
• Signs of leaking amniotic fluid vs. discharge
• Third trimester guide

When to Call Your Provider

Call any time you are unsure. Mayo Clinic says not to hesitate if you are confused about whether you are in labor. Call right away, day or night, if:

• You are under 37 weeks with any sign of preterm labor: March of Dimes lists regular or frequent contractions that make your belly tighten like a fist, a change in vaginal discharge (watery, mucus or bloody) or more of it, pelvic pressure, a constant low, dull backache, belly cramps with or without diarrhea, and your water breaking.
• You lose your mucus plug before 37 weeks: (Cleveland Clinic).
• Your water breaks, as a gush or a trickle: Mayo Clinic says to contact your healthcare team right away and go to your hospital or birthing center, even if you are not sure the fluid is amniotic fluid.
• You are bleeding: any vaginal bleeding other than light spotting (MedlinePlus), bleeding as heavy as a period (Mayo Clinic), or heavy bleeding with pain or contractions (Cleveland Clinic).
• Your baby is moving less: (MedlinePlus).
• You have regular, painful contractions: every 5 to 10 minutes for 60 minutes (MedlinePlus), or whatever timing rule your own provider gave you.

If you cannot reach your provider quickly, go to labor and delivery or the nearest emergency room, or call 911. Do not wait for your next cervical check to report a warning sign. This article is general education, not medical advice.

Frequently Asked Questions

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