nervous to have a kid?

so idk why but im kinda nervous to have a kid because i dont want to get my hopes up, I have a cousin from my grandpas side that is special ed and not that i dont love special ed kids because i work with them but i dont want to end up having a special ed kid. If i did have one, i would be eventually happy and love him/her so much. But im scared i might have one.  If you have a special ed baby, you gotta have a medical reason right? like say something goes wrong during labor and it ends up being special ed?? or ? Im confused as to why people have special ed babies when they dont have a history in the family? Can someone please tell me the reasons to have a special ed kid and does it necessarily have to me in ur family history?