Updated for 2018
The factor that has the greatest influence on breast shape and size is genetics. Your DNA affects multiple characteristics, which in turn affect breast shape and size but also changes that take place over time. In addition to the direct effect on breast shape and size, your DNA also influences hormone production and levels, which also have an influence on breast development and changes that occur during menstruation and pregnancy.
Your DNA also determines skin quality and the abundance and strength of the structural components of the breast, such as Cooper’s ligaments. Your DNA comes from both parents, so just looking to your mother and her sisters will only provide part of the picture.
Your DNA doesn’t work alone though. The actions of genetics are influenced by environmental factors. For example, poor nutrition can affect how your tissues develop and are maintained. Other factors such as smoking, excess alcohol consumption and exposure of the breast skin to UV radiation can have detrimental effects.
The breasts are comprised of glandular tissue that produces milk under hormonal stimulation and fatty tissue that fills out the remainder of the breast volume and shape. Increases or decreases in body weight will in turn increase or decrease the amount of fatty tissue in the breasts and their corresponding size.
There are secondary effects as well. A woman who has gained a large amount of weight and has had a significant increase in breast size has also increased the weight of the breasts and stretched the skin and supporting tissues of the breasts. When the weight is lost there is some “rebound” of the skin and supporting structures but commonly the rebound is less than complete and the result is some sagging. The amount of sagging depends upon how large the breasts became and how long they were that size. The rebound process of the supporting structures of the breast and the skin is slow. Most is completed by 6 months and usually no further improvement occurs after a year.
Pregnancy has similar effects on breast size as weight gain does. In this case, however, the size changes are partially driven by hormones, as the milk glands enlarge to produce milk in addition to any weight gain that takes place during pregnancy. Other than any excess weight gain, women have little control over breast changes during pregnancy; these are primarily driven by hormones. After delivery and breastfeeding is complete there is a natural reduction in breast size.
Many women experience what is referred to as “post-partum involution.” In this situation, when the woman returns to her pre-pregnancy weight there is a noticeable decrease in the size of the breasts from the size that they were prior to being pregnant. In addition to this is the stretching of the supportive structures and skin of the breast, which rarely return to their exact pre-pregnancy condition.
Brassieres have existed in some form since the 14th century BC although the brassiere that we are currently familiar with was developed prior to WWII. Brassieres are one of the best ways you can help maintain breast shape. A well-fitted bra will support the breast to combat the forces of gravity and movement. Structural tissues within the breast and the breast skin help hold the breast tissues in position and maintain shape.
Like many other tissues within the body, excessive or prolonged forces on those tissues can cause the ligaments and skin to stretch and decrease their “holding” power on breast shape. Larger breasts (and this includes during pregnancy) put more forces and stresses on the breast tissue. Wearing a well-fitting bra can reduce the forces that pull on the breast tissues and help you maintain a youthful breast shape. Finally, an appropriately fitted bra will also improve the form and shape of your breasts in your clothing.
The best way to get an appropriately fitting bra is to go to a lingerie shop where they have training and experience in fitting women for bras. Such shops tend also to have a wide selection of bras to choose from and access to additional sources if needed to get a bra that fits you well. Choosing a bra is more than just picking one out that looks pretty. It is very important that the bra fits well, and then choose one that appeals to you. Good, well made, supportive bras are not inexpensive and you may pay $70 or more for a quality bra. This is not an area to cut corners on. Often you get what you pay for.
There are many changes that happen to our bodies as we age. Some of these changes include changes to the breasts as well. Importantly, as women age, their risk of developing breast cancer increases. It is crucial that women have regular examinations and mammograms to find cancer (if it develops) as early as possible when it is most curable.
The aging process also affects the breasts in other ways. Aging causes weakening of the supportive structures of the breasts. After menopause, there are changes in hormone levels which have an impact on the glandular portion of the breasts. Post-menopausal weight changes affect the fatty component of the beasts as well.