In some cases, it may not be necessary to take off the bra completely when pushing back, especially if the shoulder strap of the bra is wide or loose, which will not hinder the pushing back operation. However, if the shoulder strap of the bra is too narrow or too tight, it may affect the push-back operation, and it may be necessary to remove the bra at this time.
Generally speaking, it depends on personal comfort and professional requirements of pushing back. If you feel uncomfortable or the pusher behind you advises you to take off your bra, then you can consider doing so.