As you get older, the breasts change, and lose elasticity and firmness. There can be many causes for these types of breast changes, including:

•     Pregnancy. During pregnancy, the ligaments that support the breasts can stretch, as the breasts become fuller and heavier. Stretching can contribute to sagging breasts after pregnancy, whether or not you breastfeed your baby.
•     Variations in weight. Changes in your weight can cause the breast skin to stretch and lose elasticity.
•     Gravity. Over time, gravity causes the sinus ligaments to stretch and become flaccid.