there's a video on youtube of Dr. Medalie performing top surgery on a guy who had had his nipples pierced in the past and Medalie decided not to resize the nipples because he was worried about the blood supply for the nipples.
In my opinion, it's not the best idea. Most people hope for the best possible results when having top surgery and a piercing might just compromise that.
Plus, if your nipples get resized, you won't be able to keep the piercing. what they do is they cut the nipple at an angle, removing one third of it, then sorta fold it down ----so the shape of the nipple is actually altered and the lower end of the piercing hole would disappear.
If you don't get your nipples resized, you'll probably not want to wear it when wearing the compression vest (till 6 weeks after surgery).