Updated: Jul 8, 2022
1 - Your family
Your genes, passed down from your family, while they decide your hair and skin colour, or height, its no surprise that they also have an impact on your bust size. It doesn't mean that you are guaranteed to be bustier if other people in your family are, but it is highly more probable compared to a family with a history of smaller bust.
“Women often are born with their breast size, but it can change in their lifetime,” Nazanin Khakpour, M.D., F.A.C.S., a surgical oncologist specializing in breast cancer at Moffitt Cancer Center, tells SELF. In short, family history is one indicator of many, and there are other factors that contribute to the fluctuations that can happen over time.
2 - Your weight
Your breasts are a complex part of your anatomy, which includes supportive or connective tissue, milk glands and ducts, and fatty tissue. How much of each tissue type you have is unique according to how your body develops. Some people have more supportive tissue than fat and vice-versa. If your breasts contain a higher concentration of fatty tissue, you could see a difference in your boob size when you gain or lose weight, Sherry Ross, M.D., a women’s health expert at Providence Saint John’s Health Center in Santa Monica, California, and author of She-ology: The Definitive Guide to Women’s Intimate Health. Period., tells SELF. That said, you probably won’t see a drastic change if you gain or lose a few pounds. “It usually has to be a significant weight gain or loss to change your breast size,” Dr. Ross says.
3 - Your workout routine
If you started your arm work-outs recently and noticed your boobs seem a little perkier, that may be related. Doing pectoral exercises can strengthen your pecs, which are four major muscles that sit behind your breast tissue and facilitate deep breathing and arm movement. If your pecs bulk up a little, this can cause your boobs to push out a tiny bit more than usual, Keep in mind that these exercises won’t actually increase your breast size—but they might grow the muscle behind the breast, which could make them appear a little bigger. Conversely, if you work-out to lose weight and experience significant or noticeable weight loss, you might notice that your boobs might be smaller or seem "saggier" due to the loss of elasticity.
4 - Your period
Your menstrual cycle can bring pretty distinct changes to your breast size, texture, and shape. Do you notice if your bust feels more tender during your menustration period? During the first half of your cycle, your body produces estrogen, in the second half of the cycle (as you get closer to your period), progesterone stimulates the formation of milk glands, which is said to cause swelling (and even a little soreness). This might prompt you to wonder why your boobs have suddenly gotten bigger. While you’re on your period, your breasts might also feel a bit lumpier than usual, but this isn’t a cause for concern. Ultimately, your breasts will return to their normal size and texture.
5 - Your birth control
Your birth control can actually impact your breast size. This is because the estrogen and progesterone in hormonal birth control cause something called edema, or water retention, and it’s unlikely to last.
6 - Your pregnancy and postpartum
Pregnancy boobs are a real phenomenon—a pregnant person’s breasts can grow several cup sizes during pregnancy thanks to hormonal changes like increases in progesterone, as your body prepares for motherhood. Though your breasts already have milk ducts, progesterone helps your body produce more ducts and lobules, which are glands that produce milk.
7 - Your age
As you grow older, you might notice that your bust will no longer be the same when you were younger. As you reach menopause, hormonal changes along the way will affect the size and shape of your breasts. When estrogen level drops as you age, the bust tissues will lose elasticity and might shrink. This will affect the perkiness of your bust and signals a firming issue, which is totally normal with age.
While it’s normal for your boobs to change, there’s often a reason behind it that you can pinpoint. But if you find that you’re experiencing sudden breast changes and you don’t know why, it’s important to talk to your doctor. While it’s likely due to something you haven’t thought of, it could be a sign of a tumor or growth in your breast. Again, don’t panic if you notice changes, but it’s best to get it checked out, just in case.