Breast development occurs in females during puberty. This development occurs in five stages, called "Tanner stages," named after Dr.Tanner, who first described them. Breast development can occur at varying ages and typically starts one to two years prior to the start of menstruation, but development generally begins between the ages of nine and 14. The stages tend to be more fluid than rigidly defined, and physicians are able to use their own judgment to determine which stage of development a girl has reached.
Stage 1
The first stage of breast development begins without any visible signs, when the ovaries start producing estrogen. This stage starts at birth and continues until the nipples and areolae start to enlarge. The breast tissue is called a "breast bud" in this stage, and in men, their breasts remain in this stage for the rest of their lives.
Stage 2
Stage 2 is when the nipples and areolae become larger, raised and a darker color. Sensitivity is increased in the nipples during this time. The breast buds are more noticeable during this stage, as well. These changes cause embarrassment to some girls because the changes may be visible through shirts.
Stage 3
This stage is somewhat general; it can vary greatly among girls, and is heavily dependent on the clinician's definition. The breasts, nipples and areolae become larger, and may cause some discomfort or pain. It is during this stage that the first menstrual period, or menarche, occurs.
Stage 4
In this stage, the nipple and areola both become raised, creating a second swelling on top of the breast. The breasts are still growing, sometimes causing discomfort, and stretch marks may appear but will fade over time. Typically, this stage occurs in late adolescence or during the early twenties.
Stage 5
In the final stage of breast development, the breast is fully formed. It becomes rounded, with only the nipple being raised. Milk ducts may start to grow during this stage, producing small lumps that typically go away within a few menstrual cycles. The last significant change in breast tissue happens around the age of 35, with the shrinking of milk ducts.
