Some do, some dont!
I think a lot of fathers do change, some for the good and some for the bad unfortunately. My SO is great with our son. He was terrified when we first found out we were pregnant but he had time to deal with it. Also, we went to a childbirth class about a month before our son was born. I think it helped him to see other fathers in the room that were a little nervous. He got to ask questions and hear what other dads were concerned about. Definitely a good idea to attend one if you're expecting!
lol kidding. Sorry.