Yes, seems to me 9 out of 10 of 'our' mums have been told they are having giants and had the fear of God punt into them at about the 30 week scan, only to give birth a more or less full term to an under 7lb perfect little sweetie.
Apparently it can be a sign of your having twins - though it's always puzzled me why they would need more to float about in when the weight of both together is often less than that of one baby ! If you happen to have two 7lb ones of course, then I can see why!
Still - I hardly think these days, they wouldn't know about multiples by now.
Anyway, otherwise although it does seem to be a feature of diabetic pregnancies according to the NHS - many apparently have this for no particular reason.
Frankly - I don't think this scan gives you anything more to worry about than you had, before you had the scan IYSWIM.