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What Causes Breasts to Get Bigger?

author image Tracii Hanes
Based in Las Vegas, Tracii Hanes is a freelance writer specializing in health and psychology with over seven years of professional experience. She got her start as a news reporter and has since focused exclusively on freelance writing, contributing to websites like Wellsphere, Education Portal and more. She holds a Bachelor of Arts in communication arts from Southwestern Oklahoma State University.
What Causes Breasts to Get Bigger?
A woman is standing on the beach in a pink sports bra. Photo Credit Wavebreakmedia Ltd/Wavebreak Media/Getty Images

Breast growth is a normal part of development for girls and women. It occurs initially during puberty and may recur throughout life due to pregnancy and weight gain. While changes in breast size are not usually harmful, they can cause physical or image-related issues for some women. Learning what causes breasts to get bigger can help women accept their breast size by gaining a clearer understanding of what is normal and healthy.


For many women, breast size plays an important role in body image. Breast implants and bras made to lift, shape and enhance the bust serve as evidence of the central role of breast size in Western fashion and culture. When it occurs rapidly or unexpectedly, breast growth can be unwanted and may even cause back pain or other physical problems. In rare instances, breast growth can signal an underlying condition like a hormonal imbalance or tumor.

Hormonal Fluctuation

A majority of the breast growth that occurs during a woman’s life can be attributed to fluctuations in the hormone estrogen. Breast development begins in girls when the ovaries mature and release estrogen, causing small buds to form. After the budding phase, breasts grow rounder and larger in response to changing hormone levels. Breast growth can also occur before menstruation as a result of water retention. Similarly, use of oral contraceptives containing estrogen can trigger breast growth in some women. Gynecomastia -- a condition that causes breast enlargement in males -- is also linked to estrogen.

Weight Gain

Breasts are composed largely of fatty tissue, making them particularly susceptible to growth when weight is gained. The amount breasts will grow as a result of weight gain varies from person to person and is not confined to women. Breast growth associated with pregnancy is generally caused by hormonal changes rather than weight gain alone. Women who breastfeed may continue to experience changes in breast size or shape, such as increased appearance of stretch marks and sagging.


For the most part, breast size is determined by genetic factors and is unchangeable without surgery. Maintaining a healthy weight by eating a balanced diet and exercising regularly can help prevent unwanted breast growth. If you experience water retention before menstruation, reducing your sodium intake can help prevent uncomfortable breast fullness. Performing exercises to strengthen the chest wall -- such as pushups and weightlifting -- may help reduce sagging and give the appearance of firmer breasts.

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