There is an ongoing debate that discusses whether or not it is safe and appropriate for women to perform any inverted postures during menstruation. With regards to yoga, many people say that inverted position such as shoulder stands, alleviate menstrual cramps and other symptoms while other say there is a potential for back flow (retrograde flow). This is still a theory, and has not yet been proven by credible research. In addition, most of the concerns people have are about staying in inverted postures for a long period of time. Ultimately, this is a personal decision and depends on your own opinion.
We have put together some simple, gentle yoga poses to ease menstrual cramps, check them here.