There are a lot of topics in the yoga world that could easily be termed "controversial". Certain issues get entirely different treatment based on the practitioner or yoga style involved. One such major issue that always comes up - eventually - is the age old question "Should women practice yoga during their period?"
There won't exactly be any ancient texts that cover this topic because for a very very long time yoga was strictly for men. You'll find groups that don't believe menstruation and yoga mix at all, groups that say it's okay to practice as long as you don't invert (go upside down), some that say just listen to your body... and just about any idea you can come up with. This topic came up in my teacher training and my teacher trainer said... if you have menstrual problems - irregular periods or reproductive issues of any kind - that you probably shouldn't do inversions while on your period, but otherwise just listen to your body.
I wholeheartedly agree with what he says, and it's the advice I give when asked. For me it's all about listening to your body just as the rest of your practice should be. I mean honestly - if you feel like you were crushed by a building on day one of your period and fine on the rest - take the one day off. If you feel pretty good but not great, do a slower practice avoiding anything too strenuous. If you're not bothered at all by the whole thing - then just keep on keepin' on. Go with the flow and do whatever feels right today.
I take it a day at a time and do whatever I feel like doing... or not. Sometimes I become an overly flexible clumsy oaf and really should pare down my usual 2 hour daily practice to 30 minutes and meditation. Other times I feel great and I just do my usual thing - complete with inversions. If the only thing you feel okay with on your period is a daily practice of child's pose - give yourself permission to do just that.
Quiet your judging thinking monkey mind and consider what you feel capable of today... make adjustments to your plan as needed. Always.