Cervical mucus plug

A cervical mucus plug (operculum) is a plug that fills and seals the cervical canal during pregnancy. It is formed by a small amount of cervical mucus.

The mucus plug acts as a protective barrier by deterring the passage of bacteria into the uterus, and contains a variety of antimicrobial agents, including immunoglobulins, and similar antimicrobial peptides to those found in nasal mucus.