Quoting Jennifer Bolen:" I went for a follow up us the other day and they said out boy is weighing 3 pounds!! My youngest is 7 ... [snip!] ... 38 weeks. So the way I see it is he's on track to be 8-9 pounds at the most? Is this what you ladies have been told as well?"
When I had an ultrasound at 36 weeks with my twins they said both girls weighed 7lbs. I delivered them the next week and one weighed 5lbs. the other weighed 6lbs. Also when I was pregnant with my daughter they said she would be 9lbs. according to ultrasound and she was only 7lbs. when she was born. So the ultrasound can be off by a little.