Here's Why You Definitely Still Need To Use A Condom During Your Period

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Every year, there are 2.8 million unwanted pregnancies in the U.S. And one of the biggest reasons for this is that people have a whole lot of misconceptions about preventing pregnancy. Along with being taught that you can't get pregnant if you're standing up or if you don't orgasm (both false, by the way), some people have been led to believe that you can't get pregnant on your period (also false, in case that was unclear). On top of that, many people have the misconception that you’re less susceptible to STIs during your period, according to a recent survey by the period-tracking app Clue and the Condom Use Research Team (CURT) at the Kinsey Institute. Taken together, these misconceptions mean that not nearly enough people are using condoms on their periods.

The study included 95,000 menstruating people (98 percent women, but also some trans men and non-binary people) from 200 countries. Twenty-one percent of them said they tended to be the ones who decided to use condoms when they had sex, while five percent said their partners were and 74 percent said it was a joint decision. So, it looks like women are playing an active role in ensuring they don't get pregnant — or at least trying to. But they're not always succeeding.

Fifteen percent of condom users didn't use them on their periods, and among them, 30 percent were less worried about pregnancy during their periods and 31 percent weren't worried about catching STIs during their periods. The problem is, you're susceptible to both pregnancy and STIs every day of the month. While there are a few days a month when you theoretically can't get pregnant, "theoretically" is the operative word there (more on that later). And your period doesn't protect you from STIs — it actually does the opposite. Here's why condom users should still keep up their routines during their periods.

You Can't Know For Sure When You're Out Of Your Fertile Window

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"A person’s fertile window (the days where sex can lead can lead to pregnancy) can overlap with their period," Anna Druet, Clue's Science and Education Manager, tells Bustle. You can estimate when your fertile window is using a period-tracking app, and this can help you figure out when the best time to conceive is. But it's not as useful for the reverse purpose. Measures like basal body temperature and luteinizing hormone (LH) urine tests call tell you when you've ovulated, but that won't necessarily predict when you will next. Most menstrual cycles are at least a little bit irregular. So, it's not possible to figure out exactly when your fertile window begins and ends. It's no wonder that about a quarter of people get pregnant after a year of using the rhythm-method.

Even If You're Out Of Your Fertile Window, The Sperm Can Survive Until You're Back In It

Sperm can live for three to five days in the womb, says Druet. So, even if you're out of your fertile window when you have sex, you could still get pregnant several days later.

Your Chance Of Getting An STI Is Greater On Your Period

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Not only does your period not prevent STIs — it actually can make you more likely to contract one. "The risk of contracting an STI from an infected partner is likely higher at certain points of your cycle, including during your luteal phase (from ovulation to your period) and during menstruation," says Druet. "This may be due to physical changes and changes in immune function during different hormonal cycle phases.”

So, moral of the story: If you use condoms to prevent either pregnancy or STIs, you need to use them during every phase of your cycle, including your period, for them to be effective. There are a lot of benefits of period sex, from cramp relief to natural lubrication, but immunity from pregnancy and STIs is not one of them.