When I was preg with my first son he had a marker in his heart and they said all these things to me like you can have more tests, and you have 1 in 1500 chance to have a baby with down syndrome. I was very worried and was crying for days. When i went to have him all the doctors said thats nothing if its only one. They only have to tell you to cover them. Obvioulsy they can't say that they baby is going to be fine but it is a small chance so try not to stress out too much.