macoms will adapt to your swelling, as long as you don’t shoot up a few back sizes, so no worries there Most girls do gain a back size in their first two weeks, due to swelling, but if your comfy in your post op bra, don’t change it, as comfort is one of the most needed things afterwards.
I measure a 30 back, but wear a 32 back (after and before my first op), I do have 34dd sports bra that I still wear, just on the tightest hook for when I’m feeling rather fat xx