Question - measurements at 19w scan

I had my anatomy scan last week at 19w2d.
I had an appointment with my OB this morning, and we went over the results.
Baby is fine, everything appears normal.
But he is BIG :doh:

His head and abdominal circumference are about 85-90th percentile!
I know guessing weight from ultrasound is not an exact science, but this was not guessing at the weight, it is the baby's actual measurements (room for error obviously but not a great deal). OB is saying at least a 4kg baby but I know that's a guess at best at this stage.
My first thought was that I have GD back again already (had it with DD) but my early glucose test is clear. DH and I were both small to average sized baby's, but our DD was 7lb3oz at nearly four weeks early. I haven't checked but I'm sure she was nowhere near that percentile at the same stage.

Has anyone else fallen on this percentile at their scan and if so how big was your baby? I am absolutely freaking out here that I'm going to end up with a you-know-what....(c/s)

Help.

My bub was looking big at the earlier scans and huge at the 34w scan (check placenta not covering cervix). But he ended up 3.53kg with head circ 36cm. He was very LONG with long legs, though. Wouldn't put too much stock in it, growth spurts/rates vary from bub to bub :)