Mucus Plug: a thick plug, comprised of mucus, which acts as a gatekeeper, protecting the uterus from infection during pregnancy. Toward the end of pregnancy, as your cervix begins to efface and dilate, this mucus plug may fall out. It’s appearance varies greatly, from stringy to thick; white, brown, or blood-tinged. The plug may fall out all at once, or gradually over days to weeks. The mucus plug may fall out before or during the onset of labor.
The terms mucus plug and bloody show are sometimes used interchangeably. They both refer to this discharge originating from the cervix, which is sometime blood-tinged, and usually comes out as the cervix effaces and dilates.