You may have heard people who take birth control say that taking the pill has made their boobs bigger. Depending on your preferences, this could be a welcome side effect or an annoying nuisance — so it's important to know what to expect. 

Here's what you need to know about how much your breasts could be affected and which birth control options are most likely to increase the size of your breasts. 

While we don't have hard scientific proof that birth control makes your boobs bigger, many people do report an increase in size, says Amy Roskin, MD, OB-GYN and Chief Medical Officer of women's telehealth provider Favor. 

Hormonal birth control contains the hormones estrogen and progesterone, which can cause water retention, leading to increased tenderness and fullness of the breasts, says Alice Sutton, MD, OB-GYN and assistant clinical professor of gynecology and reproductive science at UC San Diego. 

But just how big and full are we talking about? There's no research on the matter, however, the increase is most likely small: "Anecdotally, most people don't find that they need to change their bra size, for example, but some do report this," says Roskin. 

Moreover, if you do happen to experience an increase in breast size from birth control, the change likely isn't permanent. 

"Breasts may return to their prior size when the individual discontinues birth control," says Sutton. 

Only hormonal birth control methods will cause your boobs to potentially grow. This includes birth control pills and hormonal IUDs. 

By contrast, non-hormonal copper IUDs will not alter hormone levels or subsequent breast size, says Sutton. 

When it comes to hormonal birth control, the pill is (anecdotally) more likely to cause an increase in breast size as opposed to an IUD, Sutton says. This is because the IUD only contains progestin and no estrogen, and it only acts locally in the uterus. 

Birth control pills that contain both estrogen and progesterone result in both of the hormones circulating throughout your body, leading to potential water retention in the breasts. 

Aside from changes to your breasts, you may experience other side effects depending on the type of birth control and how you individually react to it.

Some common birth control side effects are:

Sutton says these side effects will typically occur when you first start taking birth control, and they will likely resolve after the first couple months. 

Additionally, it's important to note that birth control will slightly increase your risk of blood clots, says Sutton. Other risks that are rare but possible are:

Researchers may not have breached the topic of bigger boobs and birth control, but there are certainly plenty of anecdotal reports of this phenomenon. 

It's important to note, however, that this only happens with forms of hormonal birth control, particularly the birth control pill. Non-hormonal birth control like the copper IUD will not have this effect. 

If you do happen to experience bigger boobs when you take birth control, this side effect will likely subside when you stop taking it.