To gross out some young people who find the body gross still: humans develop a mucous plug in the cervical canal during pregnancy. Losing the mucous plug (it will fall/leak out) usually means labor. You can dislodge it during rough sex so yeah lol. If you dislodge it before 37 weeks contact your obgyn just in case.
Edit: Oh and if you dislodge it after 37 weeks you might go into labor so hopefully at this point you know what to do in that event lol