Breast Health Development

Breast development is a lifelong process that begins in the womb; healthy newborn girls’ bodies have already formed the first phase of the milk duct system. Female breasts start to grow during puberty and begin to mature when a girl begins to menstruate. Learn how the breast development process continues during menstruation, pregnancy and menopause.

Puberty: Girls’ Breast Development

During puberty, a girl’s breast development begins in response to fluctuating levels of estrogen and progesterone. During this stage of breast development (which can begin as early as 9 years of age or as late as 15), breast tissue becomes more elastic to accommodate the growth of the milk ducts. For some girls, this phase of breast growth can be painful. Once menstruation begins, usually one or two years after initial breast development, milk glands develop and breasts fully mature. The time and rate of this growth is different for every girl.

Common Breast Changes during Menstruation

Even after her breasts fully mature, a woman may experience changes due to the ebb and flow of estrogen and progesterone levels associated with menstruation. During each cycle, milk glands and ducts become larger in case of pregnancy and breasts tend to retain water. These two factors may make your breasts feel lumpy, swollen or tender during menstruation. These symptoms should subside as menstruation ceases.

Common Breast Changes during and after Pregnancy

During early pregnancy, breasts become tender, nipples often feel sore and the breasts tend to rapidly increase in size. The areola (brown or pinkish area around the nipple) becomes darker and the nipple becomes larger and more firm. These changes occur in response to changing estrogen and progesterone levels, as well as levels of prolactin and oxytocin, the two key hormones in the production of milk. Prolactin produces milk, while oxytocin delivers it. A woman will continue to produce milk until up to a few weeks or months after she stops breastfeeding. After this time, the breasts generally return to their previous size.

Common Breast Changes during and after Menopause

When a woman reaches menopause, the glandular tissue of her breasts shrinks and is replaced with fatty tissue. Her breasts may become tender, increase in size and sag due to the loss of elasticity in the connective tissue. A woman is at a greater risk of developing breast cancer as she ages, so take care of your breast health by getting regular breast cancer screenings.

Average Size of the Breast

Healthy breasts come in all shapes and sizes. Some of the main factors that influence size of the breast are age, amount of breast tissue, genetics, past pregnancies and breastfeeding and weight. Considerable variety also exists in the color and appearance of the areola and nipples.


Imaginis Corporation. (2010). Breast anatomy and physiology. Retrieved November 18, 2010, from

Massachusetts General Hospital. (n.d.) Breast development. Retrieved November 18, 2010, from

New York Presbyterian Hospital. (n.d.) Normal breast development. Retrieved November 18, 2010, from

Ohio State University Medical Center. (n.d.) Normal breast development. Retrieved November 18, 2010, from normal_breast_development/pages/index.aspx