Marathon Training while TTC

Has anyone trained for a marathon while TTC?

My doc told me I shouldn’t be running for too long when I go out, or it could impede fertility. However, I’ve never had amenorrhea, and I only run 12min miles. My longest run was a couple days before my last ovulation, but I haven’t run more than 4 miles at a time since because I’m scared I’ll ruin my chances this cycle (AF due 11/13).

I was training for what would have been my first marathon (I’ve been a consistent runner for about 7 years now) on Dec 16th, but now I think I need to focus on one or the other.

What have you done in this situation?

Thanks!