Jennifer - thats just the problem - the report says NAD - so why would they even mention it and recommend another check if it says NAD?
i just watched the video and on the video it says 2.1cm! so maybe 2.1 to them isn't something to really worry about but they thought they should mention it to play it safe???
2.1 cm is almost at the level they probably wouldn't worry about at this stage, from my incomplete memory! Mine was closer than that and I was advised I might experience some bleeding (same at the 12 week u/s) - which I never did.

I'd be fairly confident that at 32 weeks you wouldn't have anything to worry about. They probably only mentioned it because they recommended you just double check with an u/s at 32 weeks.