Does Your Uterus Really Grow During Your Period?

A photo that's been making the rounds on Facebook lately claims to show the size discrepancy between your uterus during your period and your uterus the other days of the month. "This is why we feel so heavy at the beginning of our bleed," the description reads. "Why it can feel like our uterus is about to drop out and hit the pavement (or is that just me?)." The idea that your uterus increases in size during your period makes a certain sort of sense, but does your uterus actually grow to twice its normal state? And if so, how on earth does it do that?

OK, for starters, this photo is a huge exaggeration. (Seeing is not believing in this case.) The uterus is normally the size of a pear, explains ob-gyn Sherry Ross, M.D., author of She-ology. It may get about 10 to 15 percent bigger during your period, but it certainly doesn't double in size.

So how does that smaller increase happen? Well, when you get your period, the lining of the uterus (which eventually comes out as period blood) thickens, which can lead the uterus to swell, explains Mercy gynecologist Kevin Audlin, M.D. Your uterus might also expand because your blood is flowing there to help it do its job, explains Dr. Ross.

"Women do notice a heavier sensation as the lining of the uterus thickens and blood flow increases," says Dr. Ross. "Some women have to pee more frequently during a period if the uterus starts to push against the bladder." Although you wouldn't necessarily notice this as that "feeling heavier" sensation you probably associate with your period: It may just be that you feel heavier during your period because of the accompanying rise in progesterone can lead to fluid retention and bloating, says Dr. Audlin. (And yeah, that could make it feel like your uterus was about to drop out of you.)

Your uterus only changes drastically in size when you're pregnant, not during your period, which should also make sense, since that's where the fetus grows. The more you know!