I had two hospital births. The only time something was done without my consent was to me. My blood pressure was spiking rapidly at the end of my labor with dd (firstborn), and afterward I was giving something (through an IV) to bring my blood pressure back down. I was informed as it was being given, rather than asked for my consent.
So . . . not ideal, but as far as these things go, it could have been worse. I expressed my concerns at my follow-up appointment, the doctor gave a qualified apology in that she didn't intend to avoid my consent but felt it was an emergency situation (although I don't remember feeling "off" or at risk), and with adjusting to my new life as a mama, I left it at that.
ETA: I should mention that she was a resident and I was one of her first birthing mamas, so I did give her more leeway than I would have given a more experienced doctor. On the other hand, in every other instance during my pregnancy and labor, she absolutely rocked and we got along very well. I think she just got caught up in the moment when it came to that one intervention.