I really don't know either! My earliest experience was as a ten year old using the elastic holding the sanitary pad as a catapult. There were prying eyes and resistance all around. I remember asking my elder sister who said that if there is an injury in an 'odd place' sanitary pads are used.
But yeah, I have heard women are not allowed to enter temples or worship, and stopped from many activities.

Then those living in villages(80% of India) may not be able to afford sanitary pads. :(
Talking about sex or private parts or anything related to our reproductive biology is a bane in India anyways. :)

For sure I am doing a post on this today after a brief research. Thank you @bubke for your comment!