Well, It depends on how far along you are in your pregnancy. For example, my sister's mucous plug came out when she was 35 weeks pregnant and my nephew was born about 13 days later. So I guess it depends.
It starts forming as soon as the blastocyst (5 day old baby cells) implants in the uterus. The implantation process causes the release of hormones that tells your body to start changing itself to...