We had the test done on our first child because they noticed some issues during a routine check-up during pregnancy. Needless to say my wife was a wreck until we got the results that everything was fine. Big Props to the University of Iowa's medical team on keeping my wife calm through the whole thing and providing us some free 3D images of her in the womb. Awesome place. They told us that the scanning equipment used today is so much more advanced then before that they often see things now they never saw before and so they push that panic button to be safe.
Anyways, we didn't have it done on #2 and all is well.