When I had my NT with my 3rd (at 38) my risk was 1:850, the obs told me that the risk of losing the baby because of the amnio was 1:400, we decided that for us the risk of losing a healthy baby was higher than the DS risk so we did not have it. I have a 2 friends who have lost healthy babies from amnios so felt more than a little nervous about the prospect of it.In the end it is up to what you feel comfortable with but I personally wouldn't have it in you situation.