I can of course see SP's point. If there were more people with ds around, then it would be beneficial for her child, and what mother would want anything but the most positive environment for their child?
I was offered an amniocentesis for dd, but declined due to the risk of miscarriage. I backed out on the morning of the test. Had there been a completely safe testing option, I would have taken it, but I still don't know what I would have done with a positive ds result. But it would have been my decision, made for my family and certainly not made because someone else had a positive experience, or that it would be nice for their dc to see other ds people out and about.
I know two children with ds. One is the happy, very high-functioning poster child for ds. The other has a myriad of health problems and has severe learning difficulties. You are not guaranteed the former.