My sister in law had one at 38 weeks and baby was 8 lb and his head was measuring 4 weeks. She had him at 39+3 and he was 8 lb 4 oz
I had a ultrasound at 36 weeks and my son was approximately 6lbs 10oz, but they aren't completely accurate.
I had an ultrasound at 34 my baby was measuring big at every measurment except her head was a week behind but I think her position made it hard to get an accurate reading I'm 36 weeks now hoping she doesn't get much bigger before she born