What is a normal pregnancy breast size change?

Varies . Every woman's body reacts differently to pregnancy. As one woman may gain a few cup sizes, others may only gain a half a cup size. If you are planning to breast feed, your breasts will be engorged with milk and will increase in size.
Depends. Breast size change is multifactorial. The larger the breast is to start with, the larger it gets. Smaller breasts will not increase in size as much, gaining weight increases breast size as well.