My best friend had an unexpected pregnancy at 42, and her baby girl is perfect -- but she did say the pregnancy was harder on her than the first one 10 years ago.
That said, if you're that concerned, please find a good options counselor to talk to about carrying to term (and all the great screening you can do if you're concerned about genetic issues), adoption, or terminating if that's the choice you make. Find someone who does not judge you for exploring any option you want to explore. (and dismiss all the judgement you'll probably get on DCUM on this) This is your life. Not theirs.
Also, dismiss the ridiculous PP above who chastised you about birth control and being cautious. As if you don't know anything about that.