What does your partner think? I didn't want my mum there anyway but I know my DF would have been a bit upset if he had to share such a special moment with my mum. He wanted to be the one to take care of me and hold my hand etc. If you think your mum will distract you and won't respect your wishes, don't have her there. If she gets upset, well, harsh as it sounds, that's not your problem. It's you who is giving birth and it's your choice.
My sister got all upset and offended when I told her she couldn't be at my birth. I just don't understand why other people think they have any right to even ask, if you want someone there you would ask them yourself.