Bright spot on baby’s heart

This is my first pregnancy and I just had my 20 week ultrasound. They said the baby is growing great and everything looks great except there was a bright spot on the heart which apparently can be Down syndrome. The doctor didn’t seem too concerned because my anatomy scan and another test I had done to detect Down syndrome both came back negative. They said I could schedule a level 2 ultra sound to confirm if I wanted a peace of mind but didn’t require it. But now I’m really nervous.. has this ever happened with anybody? Here is a picture. I’m waiting to find out gender until birth but the baby seems to be forming fine