No underwear, no bra. No bra in the case of an emergency per the rules at the hospital. (they are all different, so just double check) They need something that can tear away at the shoulder easily.
I hated not being able to wear a bra and underwear, but I had an epi so was in the bed at least. I think if you are going to be up and around, they might have you wear some type of underwear since you leak fluid continuously.