Gestational diabetes in 3rd pregnancy (but not in first 2pregnancies)

SB
Hi there
I am going for a glucose tolerance test in 10 days as my MW suspects GD as baby was bigger than average at 20wk scan
I didnt have GD in my previous 2 pregnancies, had a healthy weight before being pregnant, have only put on moderate weight (5 kg), eat healthily snd exercise regularly. I am in my late thirties though
Did this happen to any of you?
Thanks, getting a bit stressed!!