So scared! Please read and give imput?

I'm 31 weeks pregnant today. Had a dr appointment where he had reviewed a sonogram that I had from 2 weeks ago. He told us not to worry, but that he was required to let us know that my sons kidneys are slightly bigger then they would normally be at this point. He said it is something they see a lot now, with all the newer technology and it's nothing to get worried about. Has anyone else been told this and had a healthy baby? I'm trying not to worry but I'm just a worrier :( my dr even told me not to go home and start googling this or I would just be worrying.. Ofcourse I didn't listen. Through my search I found this may be ociated with down syndrome. Talk about terrifying. I had a screening at 13 weeks to look for signs of ds where they do an ultrasound and take a blood sample and give you a probability based off the info and your age. I'm 23 and it came out fine. If my baby was at risk for ds would there be other signs?