I was told when I got a my first horse, a rather stubborn gelding- to never work with him while on my period because he was proud cut and would try to mount me. (She was very serious)
... I was never mounted by my gelding, nor did he ever try, and he never acted any different. There are those people who seem to think such things are true.
I think if there is any chance that a horse will act differently, I would think it would be more due to your mood or demeanor changing and a sensitive horse may react to that, but that's putting a lot putting a lot of "maybes" into the equation.
I wouldn't be too worried about it !