For my first I had the blood/hormone test done. It came back with a much higher than normal chance of Downs Syndrome. I did have another ultrasound, but I opted not to have the amnio. I felt it was a risk and it wasn't goign to change my course of action. I was keeping my baby and wasn't going to risk any harm, no matter how small. I appreciated the heads-up and educated myself just in case. He didn't have Downs, but I was o.k. with the idea of it and felt prepared. Mind you - alot of people said things like, "They never know They are always wrong about those things" But the doctors/tests never said for sure he would have it. Just gave me the odds.
For my second (7 1/2 years later) I didn't even have the blood test. By then I was technically at an "advanced maternal age" of 36, but I didn't feel the need. She came out fine. But, again, I was o.k. with knowing there was always a possibility.
I just pray and trust. I felt like I will have the child I was meant to have. Now, if it were something that could have been medically fixed either right away or in utero, like a heart defect for example, I may have gone ahead with other tests. My main concern was always for the baby's safety and I considered whether a test would make a difference in my course of action. In my case, it was unnecessary.
I don't want to say it isn't stressful. No parent wants their child to have extra challenges. You just have to trust that whatever happens you were meant to be that child's mom. No matter what.