I was dilated 2 cm at my 39 week appointment at 9:00 that morning. By 3:00 I was having contractions and my DS was born at 7:30 that night - you never know what that 2 cm can turn into pretty quickly (or it could be another week!) Those numbers just don't help predict things much
I sat at 3cm for a few weeks. I think it's more common to sit at a certain level of dilation for a while with #2. When my water broke I was still between 3 and 4, but went from 4 to 9.5 in under 20 mins... so things can happen quickly once they start!
Re: 2nd time mommas- is dilation par for the course