Genetic testing

I need advice from anyone who had genetic testing done. I was tested for Down syndrome, trisomy 13/18, and a bunch of different chromosomal abnormalities. My results came back low risk across the board, I am also not a carrier for any genetic diseases. My question is, has anyone been low risk and their baby had a chromosomal/ genetic condition? Were you made aware at the anatomy scan? So nervous something is wrong even though baby seems healthy.