Natural Cycles

Natural Cycles is a contraception app that uses your basal body temperature and an algorithm to predict when you’re fertile. You take your temperature each morning with their thermometer, log it in the app, and it tells you whether you’re on a ‘green day’ (not fertile) or a ‘red day’ (fertile or possibly fertile). It’s FDA-cleared as a contraceptive method and CE-marked in Europe, which is pretty significant for a digital health app. The app works by tracking your unique cycle patterns—basal body temperature rises slightly after ovulation, so the algorithm learns your specific rhythm over time. You can use it to prevent pregnancy (avoiding unprotected sex on red days) or plan pregnancy (trying on red days). If you’re into tracking various aspects of your sexual health, Natural Cycles also lets you log sex, symptoms, and other cycle-related data. It’s subscription-based and comes with a thermometer, though you can also use their Oura Ring integration if you’re already tracking with wearables.