Ladies, you can toss out your birth control pills — maybe.

That’s what Natural Cycles, an app that tracks fertility based on body temperature and a user’s menstrual cycle, wants you to do, at least, after receiving FDA approval to market its app on Friday. The app is the first direct-to-consumer app for contraceptive use to receive FDA approval.

Here’s how it works: Natural Cycles has women use a basal body thermometer to monitor their temperature on a daily basis. The app sorts the user’s calendar into green and red days; on red days, users are told to avoid having sex, or use protection, if they don’t want to get pregnant.

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The app’s success rate isn’t perfect, however. A 1.8 percent “perfect use” failure rate, according to the FDA, means 1.8 women out of 100 will get pregnant, even when using Natural Cycles properly. The Stockholm-based company was investigated earlier this year after 37 women became pregnant while using the app, The Verge reported.

“Consumers are increasingly using digital health technologies to inform their everyday health decisions, and this new app can provide an effective method of contraception if it’s used carefully and correctly,” Dr. Terri Cornelison, assistant director for the health of women in the FDA’s Center for Devices and Radiological Health, said in a statement.  “But women should know that no form of contraception works perfectly, so an unplanned pregnancy could still result from correct usage of this device.”

Taking a birth control pill, on the other hand, is 99 percent effective, according to Planned Parenthood. But there isn’t an app for that.