Cervical dilation and effacement

What is dilation?

Dilation is the gradual opening of the cervix (the narrow, lower part of your uterus) to let your baby pass through. Dilation happens when you go into labor, and often begins even before labor starts.

During pregnancy, your cervix is fully closed to protect your developing baby. When your baby is ready to begin the journey through the birth canal, your cervix dilates from fully closed to 10 centimeters. This process can take hours, days, or even weeks. But once you hit active labor – about 6 cm dilated –  it's usually just a matter of hours before you reach full dilation.

What is effacement?

Effacement is when the cervix shortens, becoming softer and thinner in preparation for your baby's birth. During pregnancy, your cervix is about 3.5 to 4 centimeters long. As your body gets ready for labor and once labor begins, your cervix gradually thins out until it's like a sheet of paper.

Providers describe effacement as a percentage, from 0 to 100 percent. When your cervix is fully thinned, you're 100 percent effaced. Effacement happens hand-in-hand with dilation, although effacement may begin first. As with dilation, it can take weeks, days, or hours to reach full effacement.

Once your cervix is 100 percent effaced and 10 cm dilated, you're ready to start pushing your baby out into the world.

When will my cervix start to dilate and efface?

Everyone is different. If this is your first pregnancy, your cervix may not start to dilate and efface until you go into labor and contractions begin. Or it may start to efface, but not dilate. Or, your cervix may start to efface and dilate gradually over several days or weeks toward the end of your pregnancy as your body prepares for labor.

During labor, and sometimes before, your doctor or midwife may check your cervix to see how much it has effaced and dilated. He or she will do this using his or her fingers, and wearing sterile gloves.

Once your cervix has started to dilate and efface, labor is approaching. However, if you are just 1 to 2 centimeters dilated, or below 50  percent effaced, it could still be days or weeks before labor actually starts. To know when it's time to head to the hospital or birth center, you'll need to watch out for other signs of labor.

Cervical effacement symptoms

You may not feel anything when your cervix first starts to efface and dilate, especially if the process begins before you go into labor. As labor approaches, cervical effacement may be accompanied by pre-labor symptoms such as:

• Irregular contractions.  Known as Braxton Hicks contractions, these may be uncomfortable but not painful, and they come and go.
• Loss of mucus plug. As the cervix begins to efface, a plug of mucus at the entrance to the cervix is dislodged. You may notice a thick blob or gradual trickle of clear, pink or slightly bloody mucus coming out of your vagina. (If there are more than 2 tablespoons of blood, call your provider right away as this may signal a problem).
• Feeling your baby "drop." As your baby's head rests on your cervix and your cervix begins to thin, you may feel like your baby has moved lower into your pelvis. The shape of your belly may change a little too.
• Greater need to pee. As your baby's head presses down on your cervix, your uterus presses more on your bladder. You may feel the need to urinate more often. On the plus side, you may find it easier to breathe deeply once your baby moves down.

Once labor is fully underway and your cervix moves toward full effacement and dilation, you'll experience accompanying labor symptoms such as regular, more intense contractions. Your water will "break" if the amniotic sac that surrounds your baby ruptures.

What happens when I'm 1 cm dilated?

When your cervix is 1 cm dilated, it means your body is preparing for labor, or is in the very early stages of labor. It's impossible to know how quickly your cervix will dilate further. It could be a matter of hours. But it could also take a few days, or even weeks.

What happens when I'm 2 cm dilated?

As with 1 cm dilated, being 2 cm dilated doesn't mean that labor is imminent. Some women who are 2 cm dilated may go into labor within hours. Others will remain 2 cm dilated for a few days or weeks until labor progresses.

What happens when I'm 3 cm dilated?

Once your cervix reaches 3 cm dilation, you've probably entered the early stage of labor. During this stage, your cervix gradually dilates to about 6 cm. This is the longest part of labor and can take anywhere from a few hours to a few days, although between 8 to 12 hours is common.

During the early stage of labor you'll likely experience:

• Regular contractions that become progressively stronger and more frequent
• Your water breaking
• Mucousy vaginal discharge (from the dislodged mucus plug), if this didn't happen earlier.

What happens when I'm 6 cm dilated?

Once you reach about 6 cm dilation, you're in the active stage of labor. At this point your contractions become very regular, longer lasting, and more painful.

You probably won't know when you're precisely 6 cm dilated. However, as a general rule, you'll want to call your provider and possibly head to the hospital or birth center when you've had regular, painful contractions that each last about 60 seconds and occur every 5 to 7 minutes for at least an hour.

During the active stage of labor, your cervix dilates from around 6 cm to the full 10 cm. (The last part of active labor, when the cervix dilates fully from 8 to 10 cm, is called transition.) This process takes about 5 to 7 hours if you're a first-time mom, or between 2 and 4 hours if you've had a baby before. The exact duration of this stage is different for everyone.

Once your cervix is 10 cm dilated and 100 percent effaced, you're ready to start pushing. You'll probably feel a strong urge to push at this point.

What is 50 percent effaced?

When your cervix is 50 percent effaced, it's about 2 cm long. At this point, it's halfway to becoming short and thin enough to allow your baby to pass through the uterus and into the vagina. Most effacement usually happens during the first stage of labor, when your cervix is dilating to 6 cm. This process can take several hour or days, and will likely be accompanied by early signs of labor such as Braxton Hicks contractions and losing your mucus plug.

What is 60 percent effaced?

When your cervix is 60 percent effaced, it's 60 percent of the way toward becoming short and thin enough to allow your baby to pass through the uterus. Most of the effacement process happens during the early stage of labor when your cervix is dilating to 6 cm, and may take several hours or even days.

What is 70 percent effaced?

A cervix that's 70 percent effaced is 70 percent of the way toward becoming short and thin enough to allow your baby to pass through the uterus. This process typically happens during the early stage of labor when your cervix is dilating to 6 cm, and may take several hours or even days.

What is 80 percent effaced?

Once your cervix reaches 80 percent effacement, it's almost short enough to allow your baby through the uterus, assuming it is accompanied by dilation. You may reach 80 percent effacement or higher during the early stage of labor, or this may happen once you reach active labor. The same is true for 90 percent and 100 percent effacement.

Either way, effacement and dilation must both happen completely before you can begin pushing. In other words, you must be 100 percent effaced and 10 cm dilated for your baby to pass through the birth canal.

Learn more:

The stages of labor and delivery

Video: Labor and birth