I couldn't imagine NOT having my mother there.
This was my first and my partner's first child and I did all the reading and classes and felt I was as informed as I could be for going into childbirth, and to do it naturally. Once labor started, my partner didn't really know what to do to comfort me other than "you're doing great, hun". So having my mother there to focus me and ask me the right questions about the pains I was having made all the difference in the world. The nurses were fantastic as well, but having a person there that I was close with and had been through what I was going through put me at complete ease.