Myth: Preventing Pregnancy Naturally Isn’t Effective

wrote this on August 8, 2014

Many of us were brought up to believe that the only responsible and effective way to prevent pregnancy is to use hormonal contraception. I can’t say that I’m surprised. After all, the rhythm method is a widely known – and widely mocked – natural method of pregnancy prevention. And we’ve all heard that joke about it. You know the one I’m talking about. What do you call someone who uses the rhythm method? A PARENT! Hyuck, hyuck. Tired of hearing it yet? Me too. Thanks to the rhythm method, pretty much all natural methods of pregnancy prevention have gotten a pretty bad rap. And yes, there are actually other natural methods besides the rhythm method.

Sex ed classes never taught us that there’s a natural way to prevent pregnancy that is also highly effective. The sympto-thermal method of fertility awareness (or STM for short) is up to 99.6% effective when practiced properly. And, no, I’m not lying! STM is also based on reproductive science…pretty amazing stuff. The reason STM is so effective is because there is only about a six-day window during each menstrual cycle when you’re able to get pregnant. I didn’t learn this awesome little fact-nugget until I was well into my twenties!

Practicing STM requires that you monitor two things: (1) changes in your cervical fluid and (2) changes in your basal body temperature, or your waking temperature. Before you jump the gun and get super grossed out by the mention of cervical fluid, hear me out. Without this fluid, getting pregnant the good ol’ fashioned way would be just about impossible. And if you want to prevent pregnancy naturally, that’s a really good piece of info to keep in mind.


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An ovulated egg will only survive between 12 and 24 hours. Sperm can survive for about five days inside the vagina, but only in the presence of fertile cervical fluid (which is only produced during certain parts of your cycle). The acidic vaginal environment is hostile to sperm without the presence of cervical fluid, which is typically only produced around the time of ovulation. This means that when no cervical fluid is present, a pregnancy is very unlikely to occur. However, keep in mind that practicing STM requires that you follow a specific set of rules to achieve maximum effectiveness. Don’t just glance at your fluid and assume you’re a-okay.

Practicing STM also requires that you measure your basal body temperature (BBT) each morning when you wake up using a basal thermometer (you can buy one at most convenience stores). Measuring your BBT each morning lets you know when you’ve ovulated, because you’ll notice a sustained rise in temperature due to the hormone changes that occur just after you ovulate. This information is important because it helps you determine when you’re no longer able to get pregnant for the remainder of your current cycle. But, again, certain rules must be followed to accurately determine the end of your fertile phase. Measuring your BBT alone simply isn’t enough.

STM is only highly effective when practiced properly. Having unprotected sex when you’re likely to be fertile or when you know you’re fertile greatly increases your chances of experiencing an unplanned pregnancy, so STM isn’t a good fit for women who aren’t willing to strictly follow the rules of the method. Like many other methods, it also won’t protect you against sexually transmitted infections (STIs) or HIV, so make sure to take proper precautions if this is something you’re worried about.

For those who are interested in naturally preventing pregnancy and learning about how your body works, this method is both effective and incredibly empowering. So next time you hear someone say that preventing pregnancy using a natural method isn’t effective, you can kindly drop some STM knowledge bombs their way. Science, for the win.

Jennifer Aldoretta is the cofounder and CEO of Groove. She is an entrepreneur, engineer, and biohacker who is obsessed with periods, nutrition, hormones, and the microbiome.