Dilated kidney

I found out my baby boy has a dilated kidney and while the doc kept saying its common in boys and usually resolves itself before or sometimes after birth she also let me know it could be a sign of down syndrome. Has anyone else heard of this? The doctor said my other test earlier in the pregnancy was negative for down syndrome so the chance is really low but I'm still worried. Obviously it changes nothing about how I'm gonna love and Care for my son it just came as a shocker today to hear her telling me this.