The Role of the Mucus Plug in Pregnancy and Labor

Illustration of mucus plug

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If the word "mucus" initially makes you squeamish, you're not alone. But believe it or not, mucus is an important part of pregnancy.

Mucus is produced during ovulation to help sperm pass through the cervix and provide them the ideal environment before fertilizing an egg. Once this fertilization occurs, the mucus will change to seal the cervix and protect the fetus from infection.

The change results in the formation of what we call the mucus plug. Without the mucus plug, maintaining a pregnancy to term would be unlikely and, in some cases, impossible.

How the Mucus Plug Is Formed

The mucus plug is formed from secretions of cervical glands and has a thick, gelatinous consistency. The plug will begin to form when the fertilized egg implants in the wall of the uterus. When this happens, the cervix will soften and swell as mucosal cells start pumping mucus into the cavity until there are no gaps left.

Influenced by the hormone progesterone, the mucus will start to thicken and continue to be secreted on an ongoing basis so that the plug always remains fresh. Within this thick and sticky fluid are antibodies that are able to neutralize many bacteria, viruses, and other disease-causing agents.

The mucus plug will be roughly the size of a quarter and made up of around two tablespoons of mucus. It is generally a creamy to yellowish-white color and may sometimes be streaked with pink. It can also sometimes be more beige, or even brown, in color. This is not unusual and shouldn’t cause concern.

The Role of the Mucus Plug During Labor

Before labor begins, the balance of a woman’s hormones will start to change. Estrogen levels will rise as the process of fetal development nears completion. As a result, the plug will start to thin as the cervix gradually softens and dilates. During this time, there may some discharge (which is typically odorless), or the plug may come out all at once.

There may also be streaks of red or pink caused by the rupture of capillaries, which is why the loss of the mucus plug is sometimes referred to as the "bloody show."

The passing of the plug indicates that labor is nearing, regardless of the stage of pregnancy. Therefore, if the mucus plug is passed during early pregnancy, it may be the sign of impending preterm birth.

Passing the Mucus Plug

It is impossible to predict when the mucus plug will be passed as it varies from woman to woman and pregnancy to pregnancy. In many cases, the passing will be evidenced by pieces of mucus found in the woman’s panties or bedsheets. Some women may not even notice it at all, either because it was passed during urination or while showering.

There is typically little, if any, pain when the mucus plug is passed. Some women will complain of nagging pain in the lower abdomen similar to menstrual cramping, though this is less common.

When the plug is passed, it doesn’t necessarily mean that labor is imminent. At times, labor may begin in a few hours; at others, it may take several weeks.

When the mucus plug is passed, it is usually a good idea to see your doctor or midwife to ensure that everything is OK and to give you a better idea of when you can expect to deliver.

You'll also want to watch for known symptoms of imminent labor, such as lightening (when the baby drops lower into the pelvis), the beginning of regular contractions, and when your water breaks.

Losing your mucus plug also doesn’t mean that your baby is suddenly at increased risk of infection. By this stage in the pregnancy, the amniotic fluids in the gestational sac offer ample protection right up until the time your water breaks.

A Word From Verywell

Once you have lost your mucus plug, you do not need to make any special accommodations, such as avoiding sex or baths. It is only when your water breaks that you will need to go to the hospital.

However, if the passing of the plug is accompanied by heavy bleeding or a deep red discharge, call your doctor immediately, as these can be a sign of potential complications.

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