i actually found it very reassuring.
i was 35 when i had it done with ds and the reading was 1.8 (at 13wks) and then the blood work made it 1/12000 for trisonomies and 1/18000 for downs. that made me feel pretty good...and young
this time at 37 it was almost the same reading for the nuchal fold 1.7 at 12.5wks, so now just waiting on the blood work for the rest of the ips (at 15-16wks for the second set of blood work)
the tech took about 3min total to do all the work (i ask that it be done quickly - no dawdling) my lo had its legs perfectly crossed so no chance of knowing gender, but doesn't matter to me. just that the baby looked good.
oh they'll give you the crown-rump measurement and heartbeat rate too (i had mine done last tues and wrote everything down - 60mm and 167bpm)
enjoy it!