Yeah I think it's a very inaccurate. My sister at later in both her pregnancies was sent for a scan as she was measuring way too big for her dates, I think it was something like at 28 week measuring 36 weeks. Well after she had the scans she was told again with both babies that they would be just big babies and this was even after the scans. So she expected huge 9-10pound bubbas but both were born only just on 8pound. So I would try not to worry too much about it, ha ha ha I know.