Deaf or Blind baby?

I know this is a terrible thought to put in your head, but it got in mine and I had to ask. Is anyone else worried about their baby being blind or deaf? Is it something doctors would know before the baby is born? I don't know why I just got so paranoid. I was reading about how to introduce my cat to the baby and the part about the cat littter came about and how that disease can cause blindness or deafness. But regardless of that, it's not a hereditary illness so what are the chances?