During pregnancy, a mucus plug forms at the opening of the cervical canal. Its purpose is to act as a seal, blocking bacteria from entering the uterus. The loss of the mucus plug, sometimes referred to as the bloody show, is a sign that labor may soon begin.

The mucus that forms this plug is discharged as the cervix begins to dilate, or open wider, in preparation for labor. This can occur just prior to the start of labor or up to two weeks before labor will begin.

When the mucus plug is expelled, it will appear jelly-like and clear, pink, or brown in color. It may contain up to two teaspoons of blood. Any more blood than this is abnormal, and a physician should be consulted. The plug may consist of one mass of mucus, or it may emerge as a stringy or sticky substance, much like normal discharge. It may be expelled all at once or over a period of several days. The passing of the mucus plug is sometimes not even noticeable.

The loss of the mucus plug is usually not cause for concern, since it is normal in the late stages of pregnancy. It does not leave the amniotic sac vulnerable to infection, since this is still sealed until the water breaks, which will occur soon after. If the plug is lost much earlier than the due date, or if it seems to contain more than two teaspoons of blood, then a health provider should be contacted.