I was measuring ahead and it was just fluid luckily my son was born weighing 6.3oz so not a big baby at all.
At that point an ultrasound won't tell you much. It's not as accurate further along and the variation in sizes of babies that far along means even if they could give an accurate size they still wouldn't really know how far along you were. Early ultrasounds would be the best thing to go by.
Its a long story but docs and I dont know the exact due date since I had a miscarriage a month before I got pregnant again....they wont do an ultrasound to get his weight like Id prefer to see if hes big.
Just means you could have a big baby.