Well that that point, one of you is not getting what you want. You have only one life, I'd say choose your own happiness over hers. It'll probably lead to divorce if you cannot come to a compromise; it's a pretty polarizing issue.
I'm kind of in a similar situation here. At first I was on board to have a kid but over the past couple of months my mind had changed. I am not married to her but I can only imagine with her friends having kids that the subject will keep coming up, the clock is ticking. The good thing is I had a vasectomy so i'm not worried about some trickery but i'm sure she will find someone else that is willing to have a child. Sucks cause I really do care about her.
EDIT: No way in hell i'm getting a reversal either, no guarantees even if I wanted to.