text: Every woman is different. This all depends on when you hit puperty. Some girls hit puperty early and their breast will develope and continue to grow until their late teens, Others hit puperty later and their breast will not stop growing until their early 20's. Also, when a woman becomes pregnant her breast will grow larger to produce the milk needed for when the baby is born. Once she stops breast feeding and the milk dries up her breast should go back to the same size they were before she was pregnant or slightly larger.