How do I keep them from coming to the hospital when I have my baby?

You can make an announcement at a service or even in the church bulletin that you want to only have immediate family and the minister at the hospital. If at any time, you change your mind, you'll notify people on a later date individually if you would like them to come. Seeing as the birth of a baby and the first days after a baby is born is such a personal thing, no one should mind if you choose not to have people you don't want there.