Question

Both parts of my down syndrome test came back negative with my identical twin boys. However yesterday while doing their full anatomy they saw a white mark in Twin A's heart and said that is a soft mark of down syndrome but within the same phrases said not to worry since both tests came back negative. My doctor said to ease my worries to get a DNA test done(which I did that same day just to be extra sure) Now I have to wait 10 days for results and of course all I can do is worry. Has anyone has this happened?