I'm sorry to hear that, D. My husband got in a huge fight on the phone with my mom right after we got married and made her cry. (My parents claimed me on their taxes as a dependent for the year I got married, and we weren't going to be able to file as married because of it.) It was bad. She tried to convince me he was abusive for more than a year afterwards.
They didn't speak for a long time. But we've been married now six years, and I guess they're over it. Our visits are fine, and she's very happy we're having a baby.
So I guess all I can say is be a good mom, your fiance be a good dad, and your parents will hopefully come around after a while.