Baby Big in Ultrasound, But small when Born

There is an expected +/- 10% difference. My baby was estimated to be 3.8kg at 39th wk but came out 3.6kg. Considered big for a 1.5m mom but I don't have GD. Not sure if it's father's genes as my boy was also quite long in length at 54.5cm as compared to average ard 50-52cm.

My last ultrasound at wk 39 estimated my ger to be 2.85kg. When she was born at 39wks+6, she was 2.585. It shldnt differ too much though. Btw i also have GD.