Patients with big breasts usually complain about their sagginess. The operation of breast lifting called Mastopexy.  There are several reasons for sagginess of the breasts.

Age: at higher ages the amount of collagen reduces in body and this can cause sagginess.

Loosing Wight: after a harsh diet and losing weight the breasts might sag.

Pregnancy: the pregnancy put a lot of stress on breasts and can cause over growing then shrinkage that cause sagginess.

Menopause: in some women menopause might cause growth of breasts and in some it might cause shrinkage and sagginess.  In both cases some of the volume of the breast tissue can get lost.