I know someone with GD who had a c-section at 38wks due to u/s estimate of over 10lbs. Bubs was 6lbs 5oz and had to go to SCBU for a night as his breathing was a bit disorganised. Pretty grim, though he was fine after that.

I wouldn't worry about it too much at this stage. Women with GD CAN have bigger babies, but nothing is a given and until you're actually in labour it's really hard for anyone to tell how much room you have for getting a baby out anyway. They'll keep a close eye on you during labour i should think, so try not to fret just now.

Bx