Have had a pt. in labor that had it done at an early age. Usually a lot of ripping and tearing if the perineum is badly scarred(sorry to be so graphic).
The main thing to focus on is not making the pt. feel like a freak. I remember my pt. was very self-conscious about it and didn't want a big deal made about it, didn't want students, etc.. Also, of course, if a 'less-than-gentle' doc is on that day, REMIND THEM to try to be gentler with their exams, as one of the primary goals of fgm is pain with intercourse/vaginal penetration, so she's gonna need some extra TLC.
Warm compresses to the perineum throughout labor will help, maybe even put some mineral oil on the compresses prior to applying them to her bottom to help soften the skin and prevent excessive tearing. Have plenty of xylocaine ready as well as suture with smaller needles.
I'm sorry to say I don't know anything about the c/s versus vag rates for these women.
And yes, it disgusts me too, especially since it's done #1 without anesthesia #2 when the girl is like 5-10 years of age, and #3 for the express purpose of making intercourse painful. How lovely.