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Whether you have double-D breasts or were blessed on the smaller side of the lady lumps spectrum, you may have spent puberty (or even now) wondering how the F you ended up with the boobs you did. Maybe your mom didn’t have large breasts, but you and your sister have them, or maybe it’s the opposite. While genetics are scientifically proven to be one of the contributing factors that determine what size bra you wear, you may be curious as to whether or not there are other influencers. Not only do you wonder about how the size of your breasts came to be, but maybe you’re also perplexed by how much they temporarily grow each month when you’re on your period. Or maybe you are CONVINCED that your boobs got bigger after you started having sex.

We asked our weirdest boob size-related questions to Dr. Elliot Heller, board certified plastic surgeon at Allure Plastic Surgery of NYC, Manhattan, and Long Island. Find out what he told us below.


How much do genetics have to do with our breast size?

“Genetics has a lot to do with everything including breast size—if your grandmother or mother are large-breasted, you have a strong chance of having large breasts,” says Dr. Heller. “It can also be the case for small-breasted women.”

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Can breast size skip a generation?

“Absolutely,” Dr. Heller says. “Some patients come in and they state that their mom and sister have large breasts, but they have small breasts.”


How much larger do they *really* get when we have our periods?

Dr. Heller explains that some patients do not get larger during menstruating while others do. “It is not a definitive rule,” he says. “Most say they get tender and swollen during their period, so the enlargement may come from swelling. This is all due to hormone changes—breasts are very hormonally responsive.”

Why do some women’s boobs get bigger on birth control while others don’t change at all?

“Some people respond differently to hormone changes and some do not,” Dr. Heller says It also has a lot to do with breast tissue. “Breasts are made up of glands and fat—the breasts with large gland tissue will respond to the hormones, causing them to get a little larger.” He explains that ones with higher levels of fat are more likely to be less hormonally responsive.

Credit: Giphy / NBC

Is there a reason why one boob is bigger than the other?

If you have one breast that is bigger than its sister, don’t worry. It’s something that is seen very often. “90% of the population have a difference in one side or another,” says Dr. Heller. And you may find this interesting—in his experience, left-handed people will have a larger left breast while right-handers have a larger right breasts. “No one has perfectly symmetrical breasts,” he states. NOBODY!

Does having more sex make your boobs bigger?

“I think it is unlikely,” says Dr. Heller. Maybe they just *feel* bigger during sexytime?!

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How much bigger do our boobs get if we have kids?

“Pregnancy causes breast enlargement because the female body is preparing to nourish the child,” Dr. Heller explains. “The female hormones will expand the breast tissue, which is directly responsive to pregnancy hormones.” As far as size increase, it varies. “Some women will get large and some will get extremely large,” he says. Whoa!

Sleeping with a bra on, is it good or bad? Will it help with sagging in the future?

Breasts do get saggier and lose elasticity as you age. Hello, gravity! “Sleeping with a bra is good, especially after breast surgery,” says Dr. Heller. He also says that “sleeping with a bra does have a benefit to prevent sagging breasts.” Now, this has always been a controversial topic. Other experts say there isn’t much evidence supporting the idea that wearing a bra to bed can be either harmful or helpful. Some say wearing them is fine, as long as it’s a soft-cupped bra and not one with underwire. Until there’s sufficient scientific proof, it looks like the choice to wear a bra during dreamland is up to you.