I had a scan 2 days before DD2 was born... it showed a weight of 10lb 11oz. DD2 was born 8lb 13oz. Nearly 9 lb, but not close to 10lb 11oz. Her head circumference was on the higher side but she was very long at 56cm. So really the scan measures the length of the femur bone in their legs and the head circumference to come up with a weight.... so it can be totally inaccurate. FWIW... my baby was 1oz off 9lb and it wasn't a problem.