The apps are on average. And the U/s tech i think is just giving you a guesses. You will never know what you will have till he or she pops out. I am 17w 3d
i asked the lady who did my ultrasound when i thought i was 16 weeks and a few days but the baby was measuring 17w2d and she was weighing at 7oz and i asked her if that was an over weight baby=) and she said no not at all she is healthy, but im going to ask my doctor about it.