This study strives to analyze the characteristics of and changes in breast shapes of women in their 30s, whose bodies start to age and whose breasts experience changes due to internal and external factors such as pregnancy, childbearing, and breast-feeding. The analysis of the indirect breast measurements for each age group (early, mid, and late 30s) demonstrates that the volume of the breasts increases proportionally with age, the breasts lose their firmness, and the nipples start to point downwards rather than to the sides. The breast shapes experience more significant changes vertically than horizontally as the breasts start to sag downwards. The composition factors of the breasts have been classified into five factors: the level of volume in the breasts and the surrounding area, the degree of sagging in the breasts, the position and vertical width of the breasts, the volume of the breasts, and the degree of width between the breasts. The breasts have been categorized into three different shapes. Breast Shape I (32.56%) appeared most frequently among women in their mid 30s, and this shape falls into the category of Sagging I, which is one of the six breast types that have been classified by the Japanese Wacoal Research Center, in addition to Korean size 80A. Breast Shape II (38.76%) appeared most frequently among women in their mid 30s, and this shape has been categorized as flat with its size being 70A. Breast Shape III (28.68%) appeared most frequently among women in their early 30s with a conical shape and size 75A.