Buy more than one nursing bra before the birth. The bra lady might tell you to buy one now and then come back later to be fit for more once your milk comes in but don't listen to her. She means well but she clearly has forgotten how difficult it is to get out of the house with a newborn. And she fails to realize the difficulty in washing a bra while it is still on your body. And if it is off my body crazy things transpire, the likes of which are not blog appropriate.
Moral: TWO NURSING BRAS, MINIMUM.