Measuring ahead?

How many second (or third or fourth) time moms out there measured a few weeks ahead in the 3rd trimester and had it make a difference? I always measured right on track with my first and we had him full term at 7lbs10oz. This time I've felt baby grow so much more and have noticed my stomach looks much bigger earlier on and the doctor said today I'm measuring 3 weeks ahead. He said we will just keep an eye on it for the next couple visits and if they're concerned they'll do an ultrasound to check on things. I've had a feeling for a while now that she will come early but I haven't really had any medical reason to believe that. Just curious if anyone ended up having their baby early after measuring bigger?