Breasts are composed of glandular tissue, which produces milk, and a layer of fat surrounding that tissue. If either of those two tissues increase in size, such as when oestrogen levels increase the size of the glandular component, or such as when increase in weight increases the size of the fat cells in the breast then yes the breast can enlarge. If a woman maintains a consistent weight, then the breast should not enlarge in terms of the fat layer. It is possible around the time of menopause, where there are at times high levels of oestrogen, that this could make the breasts grow. However, revision surgery is seldom required, even after many years.