Cervical effacement: Causes, measuring & what it means

What is effacement in pregnancy?

Before we dive into the main question of “what does effaced mean in pregnancy”, it can be helpful to understand the different stages of labor.

The latent phase of labor is when your cervix starts to prepare for labor — sometimes called “cervical ripening”. During this process, there is increased blood flow to the cervix and release of chemicals called prostaglandins that lead to both effacement and some dilation of the cervix. You may feel some contractions during this stage, but they can be irregular. It’s usually the longest stage of labor.  

The latent phase is technically part of the first stage of labor, but it’s often separated into its own sub-division, as we’ve done here. The three stages of labor are:

• The first stage of labor includes both the early/latent phase of labor (0-6cm dilation) and active phases of labor (6-10cm dilation).
• The second stage of labor lasts from when your cervix is fully dilated, until your baby is born.
• The third stage happens when the placenta is delivered, after your baby is born [1].

Cervical effacement begins during the latent phase of labor. It describes the thinning of the cervix that happens before and during labor. During early pregnancy in the first and second trimesters, the cervix is long, firm, and closed. During the latent phase of labor, the muscles of the uterus contract. The fetal head presses into the cervix during a contraction, which causes the cervix to thin and then dilate. The mucus plug is sometimes lost during this latent phase of labor, but it’s important to note that this doesn’t necessarily mean that active labor is near — at least, not without other signs of labor, like the water breaking and regular, painful contractions.

In many first-time mothers, the cervix often thins before it opens up (meaning that effacement occurs before dilation), while it’s often the case that dilation can happen before effacement in women who’ve had children before. That’s because the cervix has previously been opened up or “stretched out”.

While this is a natural process, it can also happen in a hospital setting for those who have an induced labor. Healthcare providers use medications like prostaglandins (which are also released during natural latent labor) or special catheters known as Foley balloons to “ripen” the cervix, simulating the early stage of labor.

How is effacement measured?

Effacement is described in percentages. So if your cervix hasn’t thinned at all, it’s 0% effaced, while if it’s thinned completely, then it’s 100% effaced [2].

It can be measured by your healthcare provider or OB-GYN. Depending on where you live, they may start checking towards the end of the third term, although exactly when varies depending on your healthcare provider. In other locations, they may not perform any checks until you’re past your due date. 

If you do have these cervical checks, they can tell you both how effaced and how dilated you are. They’ll check effacement by inserting a gloved hand into your vagina and feeling how thick your cervix is — it’s not an exact science, but it can help to give both them and you an indication of where you are in the labor process.

The Bishop score is based on changes in your cervix (including dilation and effacement) and the position of your baby’s head. It’s often used when determining whether labor should be induced and how successful induction might be, based on the cervical conditions — but this will typically only be done when you reach 40 weeks [3].

Does effacement mean you’re close to labor?

Once your cervix starts to efface and dilate, it can mean that active labor is on its way. However, just how close you are to labor varies from person to person. You need to be 100% effaced and 10cm dilated before a vaginal delivery — and that can take some time to happen, especially for first-time mothers.

The latent phase — when your cervix starts to efface and dilate — typically lasts between 4 and 24 hours. However, it can last for several days or even weeks for some people, particularly for those who haven’t given birth before [4].

It’s likely you’ll experience some contractions during the latent phase of labor, but when you’re in the active phase, your contractions will become more regular, continuing until you give birth.

It’s not always easy to tell when the active phase of labor starts, so some people will want to see their healthcare provider or go to hospital for assessment. If you’re still in the latent phase (which is determined by being less than 6cm dilated and not yet very effaced), you’ll typically be advised to return home until your contractions are longer, stronger, and closer together [4].

Dilation vs. effacement

Dilation and effacement shouldn’t be conflated — but they do go hand in hand. 

While effacement refers to the thinning of the cervix, dilation is the opening or widening of the opening of the cervix. 

Effacement and dilation both start to happen during the latent phase of labor, with the cervix becoming increasingly dilated throughout the first stage of labor until it’s fully dilated and ready for birth. 

The contractions you experience during this stage help your cervix to dilate and efface, letting your baby move lower into your pelvis [5].

The cervix needs to be open to around 10cm to let the baby pass through it — and being 10cm dilated is usually called “being fully dilated” [6]. This also happens to be the typical size of a newborn baby’s head — which means that, when you reach this stage, your healthcare provider won’t be able to feel any cervix remaining around the head.

So while dilation and effacement are different, they are closely related. Research has found that the more effaced the cervix is before and during labor, the faster the process of dilation may be [7].

Once your cervix is 100% effaced and 10cm dilated, you’re ready to start pushing your baby out for a vaginal delivery. Effacement and dilation aren’t directly relevant to those having a cesarean section, but some obstetricians may dilate the cervix manually during the operation, to help the postpartum blood more easily leave the uterus [8].

Can you be effaced but not dilated?

While effacement and dilation are related, they don’t always happen at exactly the same time — which means that it’s entirely possible to be effaced but not dilated. This is especially true for first time mothers, who often experience effacement before dilation.

It’s also possible to be dilated but not effaced, which is typically more common in second-time mothers.

What are signs of effacement?

You might not feel anything as your cervix starts to efface, although you may start to feel irregular contractions. The contractions may feel uncomfortable, or they could be quite painful — it’s different for everyone, and there’s no set pattern to how many contractions you’ll get during the latent phase or how long they’ll last [5].

As you get closer to active labor, you may experience other symptoms, such as:

• Feeling your baby drop: Also known as lightening, this is when the baby’s head lowers farther down into your pelvis.
• Loss of the mucus plug: This is when the blood-tinged mucus plug that blocks your cervix during pregnancy comes away as the cervix starts to dilate, which may result in red, pink, or brown discharge.
• Your water breaking (which is when the amniotic sac around the baby breaks). This doesn’t always feel like a gush of fluid but is sometimes more like a trickle.
• Increasing contractions: As you get closer to active labor, your contractions become longer, stronger and closer together, following a more regular pattern [9].

Stages of effacement

You might hear your doctor talk about "stages of effacement”. This is measured in percentages, with the percentage increasing as birth approaches and the cervix thins.

Pre-labor, your cervix isn’t effaced, which is also described as 0% effacement. That means your cervix is the normal length (usually about 4cm) and thickness, before the process of labor begins. 

Your cervix becomes increasingly effaced as you move through the stages of labor. At 50% effaced, your cervix has thinned to half of its normal thickness.

At 100% effaced, your cervix has fully thinned out, so it feels paper thin. Complete effacement is needed for a vaginal delivery — but you also need to be dilated to 10cm to allow the baby to safely pass through the birth canal.

Are there any complications to effacement?

Usually, effacement is a normal part of pregnancy — and it’s often an exciting development, as it can mean that active labor may come fairly soon. However, if effacement doesn’t progress as expected, it’s possible that it could be a sign of a complication. Complications related to effacement include:

Early effacement or insufficient cervix

During pregnancy, the cervix usually stays closed until late in the third trimester and effacement usually happens during the last few weeks of pregnancy. But if effacement happens too early, it’s known as cervical insufficiency. This can lead to situations including:

• Second trimester miscarriage
• Preterm labor
• Preterm premature rupture of membranes (PPROM)
• Premature delivery [10]

Treatments for these conditions depend on what stage of pregnancy you’re in, how long your cervix is, and whether there is a presence or absence of broken water or an infection. Your healthcare provider will be able to recommend the best course of action for you. Statistics vary, but cervical insufficiency isn’t a very common condition [11]. You should always see your healthcare provider if you have any symptoms like abnormal spotting or bleeding, or cramps in your abdomen or pelvis during the second and early third trimester [10].

When to see a doctor

Effacement itself isn’t necessarily a reason to see a doctor. It’s a normal part of late pregnancy and is one of the first steps towards active labor. However, the timing and context of effacement matters. Effacement is normal in any of the stages of labor, but effacement before 37 weeks could be a sign of preterm labor.

It’s important to call your healthcare provider if you think you could be in labor, as well as if you have any other symptoms, such as:

• Your water breaks
• You have vaginal bleeding
• Your baby is moving less than usual
• You're less than 37 weeks pregnant and are experiencing regular contractions
• Any of your contractions last longer than 2 minutes
• You're having 6 or more contractions every 10 minutes [12]

Follow your pregnancy with Natural Cycles

Cervical effacement is a crucial step in the process of labor. Along with the dilation of the cervix, effacement gets your body ready for childbirth. The experience can vary widely (especially between first and second-time mothers), but understanding the process can help you to better understand your labor journey.

Natural Cycles can also help you to better understand your full pregnancy journey with NC° Follow Pregnancy. There’s a lot going on during pregnancy, which is why we’ve added trackers for baby movements, morning sickness, emotions, and other symptoms. We’ll be with every step of the way as you get to know your pregnancy — and your baby — better. After birth, we’ll also be there to help you on your journey to recovery with NC° Postpartum, where you’ll find articles, guides, baby feeding tracking, emotional support, and more tailored resources to support you. Learn how Natural Cycles can help you throughout your fertility journey and beyond.