Mine didn't grow much in pregnancy at all, but when my milk came in, they went HUGE and one of my first outings when I came out of hospital was to nip to Target and invest in some big boobie bras (the ones that dropped down for easy BF).

I went up a size and a cup size.

About 4 months into BF they settled down and the bigger bras got roomier, but I still wore them as they were convenient for BF.

Now my boobs have gone back to their old size, despite pregnancy, and I am back in my original size.