Final answer:
Breast size increases during pregnancy due to hormonal changes and preparation for milk production, but it is not an indication of success in breastfeeding.
Step-by-step explanation:
Breast size generally increases during pregnancy, which is a result of hormonal changes and the preparation of the mammary glands for milk production.
During pregnancy, the levels of hormones like estrogen and progesterone increase, leading to further development of the mammary tissue and enlargement of the breasts.
Increased blood volume and additional breast tissue contribute to weight gain during pregnancy, but it is not necessarily an indicator of success in breastfeeding.