Mucus plug: What is it and how do you know you've lost it during pregnancy?

What is the mucus plug?

The mucus plug is a collection of cervical mucus in your cervical canal. 

When you become pregnant, your body starts to prepare to support and nourish new life. That also includes protecting that new life from bacteria and germs. Once the egg becomes fertilized, it needs to attach to the uterine wall. As the egg implants to the uterine wall, the cervical canal begins to secrete mucus. 

The mucus secreted from the cervical canal has two main purposes:

• To trap and bind bacteria that find their way into the cervical canal
• To keep the area moist

Throughout your pregnancy, the mucus continues to collect and eventually seals the cervical canal completely. This final seal keeps bacteria on the outside from coming in and keeps it moist inside. Once the mucus has completely sealed the cervical canal, it is known as the mucus plug.

The job of the mucus plug is to remain in the cervical canal and prevent any pathogens or bacteria from entering the uterus. Several things can cause it to be dislodged early. Sometimes losing the mucus plug can indicate that you might start going into labor, but that’s not always the case. 

What does the mucus plug look like?

The mucus from the cervical canal is very thick and jelly-like, unlike the mucus from your nasal passages. You may have a clear mucus plug. Sometimes the mucus plug can be pink or even bloody.

The mucus plug is made of large glycoproteins or mucins. Mucins have much larger molecules, making the mucus very thick. The molecules are so large, in fact, that they inhibit bacteria and infections from passing through the mucus into the uterus. 

Doctors may want to give you a cervical exam in order to check the mucus plug. They will want to see if it is forming correctly in early pregnancy or if it has dislodged due to cervical expansion during late pregnancy. 

Mucus plug or discharge: how to tell the difference

Because of shifting hormones, pregnant women experience more vaginal discharge than normal. As a result, it can be difficult to tell the difference between the mucus plug and discharge.

Vaginal discharge is known as leukorrhea, and it’s usually a thin liquid that is slightly mucousy. It can range from clear to milky white and tends to have a mild smell or no smell at all. It may leave a yellowish tint on your underwear. 

The mucus plug usually looks like long, thick, stringy strands of mucus. It can be present in vaginal discharge, and it sometimes has streaks of blood in it. The blood can range from red to brown. Sometimes it comes out of the cervix in a large, blob-like volume, and other times it comes out more slowly in thick strands. 

Many people commonly call the release of the mucus plug “showing,” due to the streaks of blood and thicker mucus compared to normal vaginal discharge. Showing tends to indicate that the pregnancy is nearing the end and that labor will begin soon. 

How do you know if you’ve lost your mucus plug?

Most pregnant women can tell that they’ve lost the mucus plug by looking at the toilet paper after they’ve wiped. They may also notice the mucus plug in the lining of their underwear. 

There are a few things that can cause you to lose your mucus plug:

• Cervix softening — During the end of your pregnancy, your cervix begins to soften and expand in preparation for delivery. The cervix generally needs to be dilated to 10 centimeters before it’s ready for the baby to pass through. Your cervix can be dilated to a couple of centimeters for a few weeks before delivery. This softening can cause the mucus plug to be dislodged and come out.
• Sex — Sexual intercourse can jostle the mucus plug and make it dislodge. While it’s not harmful to have sex during pregnancy, it’s a good idea to be more careful at this time. Dislodging the mucus plug too early in pregnancy can present some risk, so if you lose your mucus plug after sex and you’re less than 37 weeks pregnant, talk to your doctor right away.
• Cervical exam — Sometimes your doctor needs to give you a cervical exam to ensure everything is moving along smoothly. The exam may jar or stretch the cervical opening. This can cause the mucus plug to fall out. If it falls out right after an exam, talk to your doctor.

If you suspect you’ve lost your mucus plug and are less than 37 weeks into your pregnancy, you should talk to your doctor. If they’re concerned that it’s too soon for you to have lost the mucus plug, they will want to perform an examination right away to check on the status of your cervix and your baby. 

If you think you may have lost your mucus plug after 37 weeks of pregnancy, then check for other signs of labor. If you don’t have any symptoms of labor or distress, then there might not be any cause for concern. It can take your cervix a few weeks to expand and dilate before you begin to feel labor pains. Losing your mucus plug is not a guarantee that labor will begin within the hour. No matter what, it’s a good idea to inform your doctor if and when you suspect you’ve lost your mucus plug.

You will likely lose your mucus plug after the 37th week of pregnancy. Sometimes this can cause you to have more vaginal discharge than normal. You may want to consider wearing a panty liner between losing your mucus plug and labor, but you certainly don’t have to pack up and head to the hospital right away. Check all of your symptoms, and talk to your doctor. If you’re not experiencing contractions or any other labor symptoms, your delivery may still be weeks away. 

The takeaway

Losing the mucus plug after 37 weeks of pregnancy is a good sign. It means that your pregnancy is progressing as normal. Although it can’t be used to determine when you will deliver your baby, it means that your body is getting ready for it. 

Some women have experienced contractions and other symptoms of labor just before or just after losing their mucus plug. Others don’t feel anything until up to three weeks later. Both of these situations are normal and healthy. 

If you have any doubts or concerns about your pregnancy or mucus plug, contact your doctor. Their goal is to keep you safe and help you have a safe and healthy pregnancy.