Is Breast Size Hereditary?
Ever wonder what determines your boob size and shape? Did you get them from your mom? Are they the result of environment, diet, or even activity level?
Well, like most body parts, the size and shape of our breasts can partly be attributed by our genes.
But that doesn’t mean that:
- They can’t change (in fact they do, quite often)
- There are no other factors that influence their size
Ever wonder "why are my breasts uneven"? We've got you covered.
Yes, Breasts Are Largely Influenced by Genetic Factors
The breast gland is composed of glandular epithelium, fibrous stroma and connective tissue surrounded by fat. How much glandular epithelium, fibrous stroma, connective tissue and fat is present depends on the circulating hormones and varies with age, menstrual cycle, pregnancy, parity and breastfeeding.
At the earlier stages of development, the breast assumes the classic, hemispheric shape. Increasing age, changes in body weight, pregnancy and lactation cause the consistency and density of the breast to change significantly.
The mature breast becomes more lax and extends down and out, assuming a somewhat flattened, pendulous shape with age. This is known as, “breast ptosis”.
Breast ptosis is a natural consequence of ageing, and varies significantly among women both in terms of degree, rate and age of onset. It is influenced by a lot of factors including: BMI (Body Mass Index), weight loss/gain, smoking, pregnancies, breastfeeding, breast size and reduction in skin elasticity that comes with ageing.
The precise determinants of breast size are largely unknown but the shape of the breast is dependent upon the ratio of adipose-to-glandular tissue, as well as the degree of support that is provided by the skin and the suspensory ligaments of the breast known as the suspensory ligaments of Cooper.
It is widely believed that the shape and size of the breast depend not only on genetic factors, but also on age, diet, number of pregnancies and menopausal status. (Breast Pathology 2nd Edition. 2017)
What Are Other Factors Associated With Breast Size?
So we know genetic factors play a big role, but what other factors are important?
Weight gain or loss is a big one. To understand this, it’s useful to know what breasts are made of. Your breasts contain fatty tissue (also known as adipose tissue).
The presence of fat tissue in the breasts means your breast size can fluctuate as you get heavier or lighter. It can also mean that individuals with higher body fat may often have a larger breast size.
What Else Causes Breast Size to Change?
While breast size is mostly determined by your genes, that doesn’t mean it stays the same throughout your life. Indeed, most women experience many changes in cup size. Here are some of the key causes of changes to your breast size (and shape).
Age: Puberty to Menopause
From puberty through maturity and into menopause, our bodies go through many changes. As we age, these developmental stages are often ushered in by hormonal changes, which can definitely affect the shape, size, and “hang” of your boobs.
Menstrual Cycle
Hormones also play a major role in your menstrual cycle, and these can cause cyclic and monthly changes to your breast size. Many women especially notice breast swelling and tenderness just before their period and/or during ovulation, which occurs around the middle of their cycle.
Hormonal Birth Control
Hormonal birth control is used for many reasons, such as menstrual cycle abnormalities and pregnancy prevention. Similar to the natural menstrual cycle hormones produced by your body, birth control can sometimes cause fluid retention and breast swelling/tenderness. These effects are often stronger in the first few months of birth control initiation and should improve with time.
Pregnancy
During pregnancy, it's normal for your breasts to potentially double or triple in size. According to the Mayo Clinic:
“One of the first signs of pregnancy is an increase in breast size. As early as two weeks after conception, your breasts start to grow and change in preparation for producing milk. Stimulated by the hormones estrogen and progesterone, the milk-producing glands inside your breasts get bigger and fatty tissue increases slightly.
By the end of your first trimester, your breasts and nipples will be noticeably larger, and they may continue growing throughout your pregnancy. Breast enlargement accounts for at least a pound of the weight you gain while pregnant.”
Your breasts may remain enlarged for a while after delivery. As for breastfeeding, research suggests that it doesn't have a negative effect on breast appearance or volume. "Don't let a fear of sagging breasts stop you from breastfeeding," the Mayo Clinic advises.
What You Can Do to Change Breast Size
So is there anything you can do to change your breast size?
Quit Smoking
Among the many health risks related to smoking is a loss of skin elasticity, which can affect the delicate skin and breast tissue. This can cause breasts to sag. Some women perceive this as a change in size, though it’s really more related to shape unless accompanied by other changes.
Maintain a Healthy Weight
Getting heavier or lighter can definitely impact the size and shape of your breasts. However, it’s worth noting that it is difficult to impossible to target body fat gain or loss to a specific body area.
Moreover, if you’re a healthy weight, we definitely don’t encourage loss or gain simply to impact the size of your breasts. Remember, if you get lighter or heavier, it will be distributed throughout your body, affecting other areas as well as breasts.
Consider the Pros & Cons of Breast Augmentation
One of the more obvious ways to alter your breast size is breast augmentation. Whether it’s breast implants or breast reduction, breast surgery will lead to a more permanent or semi-permanent change to your breast size.
Some women with larger breasts experience back and neck pain due to their breast size. So, while the reasons for breast augmentations can go beyond the cosmetic, we generally advocate discussing all the pros and cons with your healthcare provider.
Try Different Bra Styles
Different styles of wired or wireless bras promise to increase your cleavage, while others claim to minimize your breast size. It’s worth trying different styles of bra to see what makes you feel most comfortable with your silhouette and in your skin.
We strongly recommend getting properly fitted—an ill-fitting bra can make you feel really out of sorts. The wrong size or fit of bra will ruin your day, but it can also make you feel unhappy with the size and shape of your bust. The right bra can be a game-changer.
Medically reviewed by Dr. Chimsom T. Oleka, M.D, Written by Jane Flanagan — Updated on November 1, 2021.
We hope you found this post informative — but remember: we’re not doctors and this post is not medical advice! While all posts are fact-checked and well researched, we always recommend you chat with your doctor about any questions or concerns you might have regarding a medical condition. We’re here to support and educate, but never with the aim of disregarding professional medical advice you’ve been given. Phew, now that that’s out of the way, you can go on living unapologetically free.