Mucous plug?

Geraldine • 25, married with 2 kids. 3rd little monkey on its way!
I'm 37 weeks with my 3rd baby. A few days ago I noticed a reddish mucous on my toilet paper after I wiped. Maybe the size of dime. And it never happened again after that. Could it have been my mucous plug? Or from my cervical check just 3 days before? Or even from the sex 2 days before?