Well if you are measuring that much bigger your OB may induce you before your due date. I do know that sometimes when they due this they are really off. A friend of mine was induced 2 weeks early or so because they thought her baby was huge 9 pd range and well he was barely 7 pds. She was a larger woman so maybe it was harder for them to feel around.
Now, I was overdue and was told my baby would be in the low 6 pound range and she was actually 8 pds 10 ounces. Kinda different.
You have already given birth so tell us what happened.