According to this it's different -
During pregnancy, your cervical opening becomes blocked with
a thick plug of mucus that prevents bacteria from entering the uterus. When your cervix begins to loosen, this mucous plug is dislodged. Some women notice the passage of the mucous plug (what exactly is that in the toilet?), others don't (especially if you're the flush-and-rush type). Unfortunately, the discharge
of the mucous plug is in no way a reliable indicator of when labor might begin.