Why is it that babies weighing 4kgs and over at birth are considered large?

My first child weighed 4.2kgs and my DD2 weighed 4kgs.

Because my first child weighed 'so much' I have to have stupid tests done like GTT and growth scans. Yes I know I have the right to refuse them, but that just makes me have to fight more to get the birth I want.

I guess I am just venting. I am about to go and have a growth scan done that I am not happy about. My 4kg daughter was by far my easiest labour & birth and it was also my fastest (longest was DS1 - 7.5hrs, shortest DD2 - 4hrs)

Medical professionals don't care that I enjoyed the birth of my last child, nor the fact that it was 100% drug free and I was home 4hrs later. All they care about is how much she weighed and the fact they think this baby might weigh more.