High, perky breasts are a sign of youth, but time and certain life factors can take their toll. Breast ptosis (sagging) has a number of possible causes, including: Aging: The skin of the breasts and the supporting structure of the ligaments lose elasticity and become stretched as women grow older. Pregnancy: During pregnancy, increased hormone levels cause the breasts to increase in volume, often by one or two cup sizes. After childbirth and breastfeeding, the breasts may have a flattened, stretched out, droopy appearance. Significant weight loss: Overall weight loss means loss of fat volume in the breasts, as well as the rest of the body. This can result in loose skin and saggy breast tissue. Vigorous exercise without proper support: Jogging, running, or exercising vigorously without a properly fitted sports bra allows the breasts to move too freely, stretching the skin and supporting ligaments, causing the breasts to sag.