There is no definitive answer to this question since everyone's body is different. However, it is possible for breast size to increase after 30, especially if you are still menstruating and your body is producing estrogen. There are a number of factors that can affect breast size, including weight gain, pregnancy, and hormone levels. If you are not happy with the size of your breasts, there are a number of options available to you, including surgery or using a bra insert or padded bra.