My husband and I both have o- blood so why did my body attack my baby?

I had a miscarrage, from what i understand is the fetus tends to take the blood type from the fathers side. We are both o- so the baby should have been o- to so why did my body see it as a virus and kill it. I did recieve the shot in the hospital after my miscarrage but the doctor in the er was not as knowegeable as i would like him to have been and its going to be a couple days before i getinto the doctor so i am looking for anwsers here for now.