M.:
Congrats on your baby girl!
All the employees at Bosom Buddies (Park Meadows area & Westminster) have special training on fitting regular and nursing bras and you can choose from a huge selection of softcup, underwire and sleeping bras as well as nursing tanks. Sometimes the old rule of thumb "one cup size larger & one band size larger" works, but every woman is unique. Measuring is a start, but there is no standard in bra sizing, so different bras will fit differently.
The advice I've seen about needing different sizes over time is definitely true for many women. The bras you buy at 32 weeks MAY fit through the first weeks of breastfeeding, but more likely you will change enough that nursing bras you buy at 32 weeks will fit after a month or so of breastfeeding.
The bras at Bosom Buddies range in price from $18 to $58, so you have a wide selection. This is the time in your life when your bras are going to be doing heavy-duty work and you'll probably be wearing and washing them more than any other time.
The best time to buy a nursing bra? Whenever the bra you are wearing is too small, or during your last month of pregnancy.
S.