Not OP but thanks for your post, I learned a lot.

I'm trying to find out if the mattress I bought fits ASTM standards. I see that if it's bought on Amazon that may or may not be the case and mine was bought on Amazon: https://www.amazon.com/dp/B09QM5PP9Y?ref=ppx_pop_mob_ap_share

The bassinet was gifted to me and we wanted to have two mattresses so we bought one on Amazon but now your comment is making me wonder if that is the safest thing or not.