Mucus Plug Passage & Labor Progress: What Does It Mean?

Question
I am 20. I have one daughter, 21 months old. December 2 or 3, 2003 is the date of my last period. I am 38 weeks and 4 days pregnant.

what does it usually mean when you pass your mucus plug? I went to the hospital last night with strong contractions 4 1/2 minutes apart, but they weren't changing my cervix .  I am currently (as far as last night) 2 cm, beginning to thin, my cervix is fully ripe, and the baby is at a -1 position.  What of this could cause my plug to pass and what does it mean in relevence of time until delivery?

Answer
As the cervix starts to dilate, your cervical plug starts to come out ("bloody show"). It sometimes indicates that you may go into labor in a few days or in a few weeks. It depends on how often you have contractions, where the contractions are, and how long each contraction lasts. When you have contractions at the level of your belly button, and the contracts less than every 5 minutes and each on lasts for at least 45 seconds in length, and this goes on for an hour, I would ask to be checked again. If your cervix is cilated more than 3-4 centimeters, you are considered to be in labor.