The mucus plug is the small amount of thickened mucus that blocks the cervical canal, which leads up into the uterus.  When you lose your plug you may see an actual clump of mucus, or you may just notice an increased mucus discharge.  The mucus may be lightly tinged brownish, pink or red when it is expelled.  This is referred to as bloody show.

Labor may begin soon after the mucus plug is discharged;  however, it can begin as much as 1 to two weeks later.  If you lose your mucus plug, you should watch for other signs of labor, including a mild swelling that may occur in the last 2 weeks of pregnancy as your body builds up fluids for labor.  Also, as labor approaches, you may feel more braxton-hicks or pre-labor contractions. 

Unfortunately, there is no way to predict with any certainty when labor will start.  Even your due date is only a best guess;  your baby is going to be born when it is good and ready!

Will labor start when I lose my mucus plug?