Hi - just to reframe this a bit - the test doesn't actually test for genetic conditions, it tests for the statistical liklihood of your baby's risk for these conditions. So your testing shows and elevated risk for your age - can you share what that risk number is? Normally it's presented as "1 in 2,500" or "1 in 200" or even lower. When they combine this screening with the ultrasound, they'll be able to look at your blood test and soft markers on the u/s to determine your risk with greater precision.
I had some elevated risks with three of my four pregnancies. In my first pregnancy, the blood test was fine (this was 15 years ago so it was a triple-screen back then) but he had some abnormalities on his u/s that indicated an increased risk of Trisomy-18, a condition that is very often "incompatible with life." I opted for amnio and he was fine.
In my second pregnancy, the blood test (a quad screen at that point) came back with a 1 in 200 risk for Down Symdrome. I wouldn't have terminated but am someone who needs to know everything and be prepared for things, so I again had amnio and he was fine.
With my twin pregnancy when I was a surrogate, the quad screen showed a 1 in 5,000 chance of any problems, which is better than normal so no worries. However, the u/s showed a calcium spot on the baby boy's heart, which correlates to a risk that's double what the blood work showed, so 1 in 2,500. Still better than the average risk so we didn't take any action. He was fine as well.
The u/s will be a much better tool in assessing whether or not your baby has any health issues. Getting blood screenings that indicate an elevated risk is very common and in most cases, the risk turns out to be nothing and the baby is perfectly healthy. At the u/s they'll look for the thickness of the NT fold, the presence of a nasal bridge bone, the length of the femur, any abnormalities of the heart and spine, etc. and if all of those check out, there is a very good chance that your baby is fine but amnio is always an option to know for sure. Your doctor will be able to talk about the miscarriage risks of amnio compared to your baby's risk of DS after the u/s is done.
It's a nerve wracking time for sure - I hope you get some good news after the u/s.