Understanding Cervical Dilation, Effacement, and Fetal Station: A Guide for Expectant Mothers

It can be a little nerve-racking to have terms like “dilation,” “effacement,” and “fetal station” thrown at you when you’re already dealing with the difficulties of pregnancy, so we’ve compiled a guide for you.

Read on to learn more about how your body prepares for labor and what you can do to make the process more manageable.

Dilation refers to the gradual opening of your cervix, which is the lower, narrow part of your uterus that connects to your vagina. Your body will usually start this process late in your third trimester, when it’s almost time for you to give birth (although it sometimes starts earlier, with preterm deliveries).

Doctors measure cervical dilation in centimeters, not inches. Your cervix will start at a tightly closed 0 centimeters, eventually expanding to a much wider 10 centimeters. Once you hit that 10-centimeter mark, you’re fully dilated and can start pushing. 1

Cervical size comparisons

If you have trouble picturing things in centimeters, you can visualize how wide your cervix will be throughout the process by comparing it to various objects:

• 0.5 cm: Pea
• 1 cm: Cheerio
• 2 cm: Nickel
• 3 cm: Grape
• 4 cm: Ping-pong ball or a banana slice
• 5 cm: Golf ball or Oreo cookie
• 6 cm: Baseball or tomato
• 7 cm: Soda can top or orange
• 8 cm: Coffee mug or donut
• 9 cm: Softball or medium-sized pancake
• 10 cm: Grapefruit or bagel

Cervical effacement

Your cervix needs to soften, shorten, and thin itself before dilating. This is called effacement (ripening).

Unlike dilation, doctors track effacement in percentages, from 0% (no thinning) to 100% (completely thinned out). At that point, the cervix is usually paper-thin.

Normally, your cervix is around three to four centimeters long during pregnancy, but it will shorten to about two centimeters once it’s 50% effaced. It needs to be completely effaced for a vaginal birth. 2 3

Together, both processes (effacement and dilation) prepare your cervix for childbirth.

Fetal station

Fetal station refers to how low your baby is in the birth canal. Your doctor will check where your baby’s presenting part (the part that leads the way through the birth canal, usually the head) is in your pelvis. 4

Once you’re admitted to the hospital, your doctor will measure how low your baby is, as follows: 4

• -5 to -1: At this stage, your baby is still above your pelvis, before “lightening” (when she finally drops to the bottom of your pelvis).
• 0 station: This is when your baby’s head draws even with your ischial spines (the narrowest part of your pelvis).
• +1 to +3: Once your baby’s presenting part passes the ischial spines (usually during the pushing stage of labor), your doctor will number it from +1 to +3. At +3, your baby’s head will be crowning. 5

Often, your cervix will start to efface several hours or days before you go into labor, with dilation following.

However, both processes can start “early” (potentially as early as a few weeks before childbirth). Sometimes, the cervix dilates up to four centimeters weeks in advance of the onset of labor. 6

Your cervix might take a few hours to a few days to efface. It may take longer if it’s your first time, which means that it can delay your dilation and prolong your labor. 3

If you’re a first-time mom, it’ll probably take about 8–18 hours to dilate once you start labor, but it can happen more quickly (5–12 hours), particularly if it’s your second or third pregnancy. It could even last longer if your doctor induces labor. 7

None of this is universally true, since every mom-to-be is different. In fact, dilation-and-effacement isn’t always a neat, two-step process. You may actually dilate a little, efface, and then dilate again up until childbirth. That’s also more likely if this isn’t your first pregnancy. 8 9

You may notice the following signs that this process is underway:

Lightening

As you get further along in your pregnancy, your baby will eventually descend lower into your pelvis, known as “lightening.” When it happens, you may feel that you can breathe more easily as your baby stops putting pressure on your lungs.

However, you may now have to contend with discomfort in your lower abdomen as a result of your baby’s new position, and it could make you need to pee more often than before. 10

As mentioned, your baby could drop into your pelvis as early as week 36 of your pregnancy, though it could also be later. 4

Loss of the mucus plug

To protect your cervix from bacteria and infection, your body grows a jelly-like substance in the cervical canal, known as a mucus plug. This mucus slips free when your cervix softens and opens, leading to vaginal discharge that is usually off-white or transparent. 11

Losing your mucus plug doesn’t always mean that you’re immediately going into labor, although it’s a sign your body is preparing for it. Note that instead of seeing it all at once, you may experience an increase in mucousy pregnancy discharge lasting several days or weeks. 12

What’s the difference between losing your mucus plug and seeing bloody show?

As you approach labor, your discharge may also be tinged with blood. This may cause pinkish or brown discharge during you pregnancy, which is known as “bloody show.” 13

While it sounds similar to losing your mucus plug, it’s actually different. Bloody show appears closer to labor and means that your cervix may be dilating. That isn’t guaranteed, but it is fairly likely. 11

Contractions

If you want more definitive signs of labor, wait for contractions that gradually increase in intensity, frequency, and duration. These thin and open your cervix, encouraging your baby to move through the birth canal. 14

Unsurprisingly, this process can be painful. Talk to your doctor about pain management options.

By your third trimester, you’ll also probably be familiar with false labor contractions, known as “practice” or Braxton Hicks contractions. These are irregular and uncomfortable but not painful, resembling mild menstrual cramps or abdominal tightening. These don’t affect your cervix or result in effacement or dilation. 15

If you have difficulty distinguishing between true and false labor pains, use a contraction timer in a pregnancy tracker app to get a better idea of the frequency and duration of your contractions.

Sometimes, your cervix might not dilate on schedule. This can happen for various reasons, but regardless, the solution is the same—if it’s about time for you to go into labor but your cervix doesn’t seem to be behaving, you should contact your doctor.

How can your doctor help you dilate and efface?

In some cases, your doctor might take a wait-and-see approach, but they also might intervene and induce labor when it’s not happening naturally.

If you don’t go into labor naturally by week 41 of your pregnancy, or if a medical issue like high blood pressure crops up before then, your doctor is more likely to opt for induction to reduce the risk of complications like stillbirth or your baby not tolerating the delivery process well.

There are several methods of labor induction: 16

Medication

Your doctor may use a drug like synthetic oxytocin (Pitocin) to stimulate contractions. 17 You may also need prostaglandins (cytotec or cervidil) to ripen the cervix and induce labor. 18

Mechanical induction

It’s also possible your doctor will be able to hurry things along with one of these mechanical methods:

• Membrane sweep or strip: They’ll use their gloved fingers to separate the amniotic sac from the cervix, stimulating the release of hormones and encouraging labor to begin.
• Foley catheter (Foley bulb): Your doctor may use a catheter to insert a deflated balloon into your cervix. Once the balloon is inside, they’ll carefully inflate it, encouraging your cervix to open. 16
• Amniotomy: If your water doesn’t break on its own, your doctor may also manually rupture the amniotic sac using a small plastic hook, which jump-starts the process. 16

Your doctor can sweep or strip your membranes in their office, but if they use a Foley bulb or perform an amniotomy, that will need to be done in the hospital.

Regardless of which procedure your doctor opts for, they’re all generally very safe and haven’t been shown to increase your risk of needing a C-section delivery.

There are several at-home methods that are purported to kickstart labor (which, by definition, would require stimulating effacement and dilation). Note that these haven’t been well-studied, and they’re firmly in the realm of folk wisdom rather than evidence-based medicine.

With that said, they include: 19 20

• Stimulating your nipples: Similarly, using your hands or a breastfeeding pump on your nipples can produce oxytocin, which may stimulate contractions.
• Having sex: There’s another common belief that you can boost your oxytocin levels if you orgasm.
• Staying active: Light exercises like walking and rocking back and forth on an exercise ball (birthing ball) or even laughing can supposedly help you dilate.

Generally, all of these methods are safe, and while they might not work, there’s no harm in trying them—as long as your doctor says it’s OK. However, consult with them first, and always follow their advice.

Note that you shouldn’t try to measure your own dilation at home. Attempting to perform a self-check risks introducing bacteria into your vagina, and you might not even be able to feel the cervix. Just leave this process to your doctor.

While you may be excited to meet your baby, your body will decide when it’s ready for cervical dilation and effacement—and, consequently, for labor. The best approach is to stay informed, listen to your body, and work closely with your doctor to ensure a safe and healthy delivery.