I had an amnio with my 2nd pregnancy. I was 39, had a borderline nuchal which came me a high risk factor of 1:92. We were offered CVS or amnio, or of course do nothing.
The risk for CVS was higher than amnio, and after looking into it, discovered that the risk factors they give are generalised, and that actually the doctors carrying out the procedures generally have near perfect track records, so statistically, the risk of cm is much lower.
For me I had to know what we were dealing with. Was there a problem or not. Otherwise my pregnancy would have been stressful and full of angst. Thankfully, everything was fine. If we had had a bad result, I'm not sure what we would have done, and I guess we'll never know and I try not to think of that now.
That actual procedure is quite surreal and emotive. You are covered in a theatre gown and swabbed with iodine. They take a scan to check where the baby is and then decide if they can go ahead. The weirdest hung is watching the needle on the screen trying to break through the amniotic sac. But it's over with quite quickly and you don't really bleed! Ou have to keep quite still and relaxed for 24 hours after the procedure. My DH took our dd1 away to his folks for the weekend, and i literally lay on the sofa all weekend with lots of TV dinners and the remote/magazines.
It was actually quite relaxing and oddly enough, I felt dd2 kick/move for the first time that night, which heartened me. The results came back v quickly (procedure some on the Fri, initial results on the Mon) so it wasn't too torturous.
Beat of luck whatever you decide. It isn't easy.