The Role of the Mucus Plug in Pregnancy and Labor

Mucus Plug
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Mucus is an important part of pregnancy. It is produced during ovulation to help sperm pass through the cervix and provide them the ideal environment in which to thrive. Once the egg is fertilized, the mucus will change to seal the cervix and protect the fetus from infection.

The latter process results in the formation of what we call the mucus plug. Without this, 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.

Under influence of 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 the viscous fluid are antibodies able to neutralize many bacteria, viruses, and other disease-causing agents.

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

The Role of 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. Under the influence of this hormone, the plug will start to thin as the cervix gradually softens and dilates. During this time, there may some discharge, 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. It is for the reason that some people refer to the process as the "bloody show."

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

Passing of the Mucus Plug

It is impossible to predict when the mucus plug will be passed; it varies from woman to woman. 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 when showering.

There is typically little, if any, pain when the mucus plug is passed. Some women will complain of a nagging pain in the lower abdomen similar to that of menstruation, although 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 it is passed, it is usually a good idea to see your doctor to ensure that everything is okay and to give you a better idea as to the delivery date.

Losing your mucus plug 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 when your water breaks.

A Word From Verywell

Once you have lost your mucus plug, you do not need to make any special accommodations. There is no need to avoid 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.​

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Article Sources

  • Becher. N.; Adams-Waldorf, K.; Hein, M. et al. The Cervical Mucus Plug: Structured Review of the Literature. Acta Obstet Gynecol Scand. 2009; 88(5):502-13.