Hello tryingtobehopeful, I am so sorry to hear that you are in this position, and just wanting to add my support for the tough decision ahead, and to try to help by telling you my story.
I was not pregnant with twins, but at 11.5 weeks had a nuchal above 5 for my first second pg after a m/c. We decided to go ahead with the CVS the next day, having been given a 1:2 chance of Down's. In our case, although we prayed it would not be the case, the result was confirmed two days after the CVS, as positive.
Because the predicted chance of Down's for us was so high, our decision to have the CVS seemed straightforward to make. The risk was described as 1-2% loss from the procedure. I am not sure if this is adjusted if twin pregnancy.
Looking back, we were treated with great care and sensitivity by the nurses, who did their best to make it as comfortable as possible. The actual insertion of the needle, and sampling probably lasted about 3-4 minutes with some sensation of movement and discomfort but not intense pain. It felt longer, but I recovered very quickly.
Emotionally, I found the procedure terrifying, but not as painful as I thought it might be, and dp was with me throughout.
The relief of finding out just what was causing the high reading was a strong motivator for us to proceed, despite the risk, we just couldn't carry on without knowing. The procedure is quickly forgotten as the main focus is, of course, the outcome.
I am so much hoping you will have a positive outcome if you go ahead. I know how much bewilderment and distress you must feel in your situation. Seek all the help and knowledge you can. Bear in mind that Nuchal scores, as with all human measurement can be inaccurate. I am sure you will make the choice that is right for you and your babies. x