In some cases after puberty the two breasts differ in size and do not improve with age. It is common for the two previously symmetrical breasts to change in size after childbirth. In extreme cases such as Poland syndrome one of the breast may be completely absent.
Procedures focused on correcting breast asymmetry vary depending on the type of correction needed, the larger breast may be reduced or the smaller one may be augmented to match the other, both breasts can be corrected at once also.