The passing of the mucus plug, which is clinically known as "bloody show," indicates that the cervix is dilating; this is a sign of impending labor. Bloody show can occur anywhere from a few hours before the onset of labor to a few weeks. The cervix opens gradually, causing the mucus plug that had previously blocked the opening during the pregnancy to be expelled, according to the American Pregnancy Association.
The mucus plug serves to blocks the cervical opening and keep bacteria from finding its way into the uterus, notes the American Pregnancy Association. The plug must be expelled to allow the baby to pass from the cervix during childbirth.
Bloody show is generally clear, although it may have a slightly pink tinge to its color, according to the American Pregnancy Association. It may also present as a sticky discharge or stringy mucus, and it may go completely unnoticed by some women. There is usually no need to contact a healthcare professional about the passage of the mucus plug unless there is bright red blood or the discharge appears to be more than a few tablespoons of fluid. These symptoms may indicate complications that need to be addressed right away.