Nature has made breastmilk in such a way that it will change according to the baby s needs and your bodily changes. So it will not affect breastmilk. However some research says that breastmilk turns thin in consistency during periods so u can expect the baby to feed often due to shorter satiety levels.

I have read that there will be a dip in milk supply during periods. Not sure. But don't worry much about this. Take enough rest, sleep more and feed on demand.