I don't think it compares to a WOD - it really is more like a marathon, when going through an unmedicated labour. Hours upon hours (and in my case, days) of contractions, the "wall" hits where you see no end in sight, the thought of "why the hell did I sign up for this", knowing the finish line is ahead but not knowing when, the endless endurance. Yes, a WOD is like that, but in a much briefer time span and there are some additional psychological components to it.
Unlike a WOD or marathon though, you simply can't run away from it, even if it comes down to medication or an emergency c-section, there is no turning back, and when it is over, you should be proud no matter how it was achieved
I need to keep this in mind as I am 6.5 months and going through the "why the hell did I sign up for this... again!" mentality. This time, I will be at home instead of the hospital, to hopefully provide some more mental support through it. I hated the hospital.