I wear apx the same size I did prepregnancy (DDD-DDDD)... BUT the big difference for me is that the girls have gone south for the duration. We're talking old lady jokes about tucking breasts into their belt kinda thing ;) It's not that bad... but they blew UP (bigger than my head) with engorgement, and then while nursing they were firm and "up" from the milk, but post nursing they just deflated. Seriously. They dropped about 3 inches if I'm being objective, but it LOOKS like 6 inches.
The bras I wear are the same SIZE, but they're different in structure. I now require a certain kind of bra (underwire demi) to keep the girls "UP! UP! UP! Where you BELONG!"
I also have to "aim" my nipples in the correct direction, and adjust as I get in my bra the extra skin. Ewww. That sounds grosser than it actually is. It's just a 'deflated' issue. They're BIG, but the deflating means they can move in any direction, so I need to corral them into place.
I didn't have to be so choosy about structure, and materials, and (cough) support pre-pregnancy.