Cervical Dilation: A Key Labor Sign

When you’re nearing the end of pregnancy, every twinge and tightening can feel like a potential sign of labor. One of the biggest indicators that your baby is getting ready to make their grand entrance is cervical dilation...a sign of labor that isn’t exactly in plain sight. So, what exactly is cervical dilation and how will you know it’s happening? Let’s break it down.

What is the cervix—and what does it do?

The cervix is a small but mighty part of the female reproductive system. It’s a cylinder-shaped tissue that connects the uterus to the vagina, acting as a protective gateway. Throughout pregnancy, the cervix remains closed and firm, keeping your baby safe inside the womb. As labor approaches, the cervix gradually softens, shortens, and dilates (opens) to allow your baby to pass through during delivery.

What is cervical dilation?

Cervical dilation refers to the gradual opening of the cervix. Measured in centimeters, your cervix must open to 10 cm before your baby can be born. You know those labor pains you’ve been dreading? Those uterine contractions drive the cervical dilation process, helping to the open the cervix and move your baby down into the birth canal.

When does cervical dilation start?

When cervical dilation kicks off is going to vary from person to person. For some, dilation can begin weeks before labor, while others may not start dilating until active labor. Factors like the number of previous pregnancies and individual anatomy can influence the timing.

How long does cervical dilation last?

Dilation isn’t a uniform process. Some may dilate slowly over several weeks, while others progress rapidly within a few hours. The first stage of labor (0 to 3 cm) can be slow and unpredictable. But dilation tends to speed up during active labor (4 to 7 cm) and moves rapidly (about 1.2 to 1.5 cm per hour) during the transition phase (8 to 10 cm).

What are signs of cervical dilation?

Signs that your cervix is dilating can vary from subtle to unmistakable. Here are a few key indicators:

• Regular contractions: As your cervix dilates, you may notice contractions become more consistent, painful, and closer together.
• Bloody show: As the cervix begins to open, small blood vessels may rupture, causing pink or blood-tinged mucus (this is sometimes referred to as losing your mucus plug).
• Pelvic pressure: Some people experience a heavy, aching sensation in the pelvis or pressure in the vaginal area as dilation progresses.

Can you check to see if your cervix is dilated?

While you may be curious about checking yourself, it’s best to leave cervical checks to your healthcare team! Self-checks (inserting your fingers into your vagina to feel your cervix) are not recommended without medical guidance, as they can increase the risk of infection or cause discomfort.

However, there is a non-invasive method you could try! The “purple line method” involves looking for a purple-ish line near your natal cleft (to put it indelicately, your butt crack). Research has shown that this line appears during active labor for about 75% of pregnant folks. The idea is that the further the line moves away from your booty and closer to your lower back, the more imminent labor is.  

How dilated should you be at the end of pregnancy?

At the very end of pregnancy, the cervix may remain minimally dilated (1 to 3 cm) until labor begins. For those who have had previous births, it’s not uncommon to be slightly dilated before labor kicks off. But remember, dilation is just one part of the labor equation, and other factors like cervical effacement and fetal position come into play.

Cervical Dilation Chart

Here’s help visualizing how your cervix is changing during dilation:

• 1 cm: Small, like a pea
• 2 cm: Similar to a grape
• 3 cm: About the size of a walnut
• 4 cm: Comparable to a lime
• 5 cm: Roughly the size of a small orange
• 6 cm: The size of a large kiwi
• 7 cm: About as big as an orange
• 8 cm: Similar to a grapefruit
• 9 cm: Comparable to a donut
• 10 cm: The size of a large bagel

When to Contact Your Doctor About Cervical Dilation

Reach out to your healthcare provider if:

• Contractions are frequent and painful (occurring every 5 minutes, lasting 1 minute, for 1 hour)
• You experience heavy bleeding
• Your water breaks
  
• Baby movements decrease

Knowing the signs of cervical dilation can help you feel more prepared and in control as you approach your due date. And if you have any concerns, don’t hesitate to reach out to your provider!

More on Labor and Delivery:

• Natural Ways to Induce Labor: Fact vs Fiction
• Labor Relaxation Techniques: Tips for an Easier Birth
• How to Write a Birth Plan (Plus, Free Birth Plan Templates!)
• Perineal Massage—Does It Really Help?

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REFERENCES

• American College of Obstetricians and Gynecologists. (2023). Preterm Labor and Birth.
  
• American College of Obstetricians and Gynecologists. (2023). How to Tell When Labor Begins.
  
• StatPearls. (2023). Cervical Insufficiency. National Center for Biotechnology Information.
  
• StatPearls. (2023). Cervical Ripening. National Center for Biotechnology Information.
  
• Shephard, E. (2018). Normal Cervical Effacement in Term Labor. American Journal of Perinatology.
  
• Cleveland Clinic. (2023). Labor and Delivery.
  
• ScienceDirect. (2023). The Purple Line as an Indicator of Cervical Dilation During Labor.
  

Disclaimer: The information on our site is NOT medical advice for any specific person or condition. It is only meant as general information. If you have any medical questions and concerns about your child or yourself, please contact your health provider.