It will massively affect your performance. Incredible really that sports will pump millions into making a bike that weighs a few grams less or into devising a diet for optimum performance but don't put the same effort into devising ways to mitigate the negative effects of the menstrual cycle. Perhaps they do but we don't hear about it because periods are still a bit taboo.
I know lots of elite athletes with low body fat don't have periods, and you can take meds that postpone your period, but I'd be interested to know if it's just something women athletes develop their own way of dealing with or if it's a specialist field of study now.