Mucus plug or Mucous plug is a plug which stops the entering of bacteria and other diseases through the cervix and entering the uterus. It is a kind of a protective shield. It is a plug which stops the opening of the cervix. The mucus plug is diluted when the woman is about is about to give birth. The mucus plug stays throughout the pregnancy. The mucus plug is clear or a little pink in colour. It may be quite sticky as well. The mucus plug is also known as a Bloody Show as it may be covered in blood.