I only wore a bra to keep the breast pads in place, and I still had to sleep on a towel anyway (which was soaked every morning, lovely). Unfortunately, I did sleep a bit oddly one night and ended up with my first bout of mastitis. Could have been position, but it could have been the bra as well. I certainly didn't wear one overnight after that! I'd say don't bother if you're not comfortable as well.