I also got a pass in Ob/Gyn (and peds) but I was NEVER asked about it. Don't worry about it man. If your record shows a pattern that you've worked hard and done well, that's all that matters. One grade won't kill you. Remember, they look at the forest, NOT ONE TREE. They would probably NEVER ask you, but if some jerk brings it up, don't come up with an excuse. Just say you worked just as hard in ob/gyn as in any other rotation and learned just as much...you just got a pass. Never use excuses during interviews, even if it's a legitimate one. Just my 2 cents.