I definitely feel healthier and more relaxed when I do yoga daily so I think it could only hurt to stop doing those activities right when my body needed relaxation.
Lisa, I definitely agree, and if anything the stress reduction aspects of yoga are even more beneficial during this time. I was just discussing this with my own yoga teacher (in fact I interviewed her on my blog
recently and we talked about exactly this, hope it's ok to link to that here.)
It's interesting because women didn't practice yoga until the last 100 years or so (am also reading an excellent book on the history of yoga BTW called The Subtle Body for anyone interested), and when it was introduced to women a lot of cultural biases and misunderstandings were introduced, including the idea that inversions caused flow problems. Medically, that's been proven not to be the case. Energetically, in terms of the flow of upana - our natural 'releasing' energy (prana being its counterpart) - there is still the idea that our body is trying to release during menstruation, and that inverting may take that energy up into our belly area, which is the 'fire' area, which could throw off the energetic release, either causing us too release too much or too little upana. But many women have found that light inversions, and certainly a full yoga practice, are very beneficial at this time. So I think it is about trusting and feeling what is right for our body, which yoga really helps us tune into.