Katherine spends 30 seconds each morning with a thermometer under her tongue. She takes her temperature and notes the result in an app on her phone. After a minute, her screen will beam one of two colours: crimson or bright emerald. The latter lets her know that she isn’t fertile. The former means that she is, and ought to use protection if she’s having sex that day. The 30-year-old is using Natural Cycles; the first birth control app approved by America’s FDA. Think of it working like a standard period-tracker app, only powered by a very personal kind of algorithm.
Natural Cycles allows its users to either plan a pregnancy or prevent it, with prevention the most popular use among young women. There are a few intricacies (and disclaimers) about the app you should know about first, though. A user’s basal temperature – or the warmth of the body when it is fully at rest – must be recorded as soon as they wake up each morning. That means no snoozing your alarm. You can’t have a drink, leave your bed, or even move from your pillow before taking a reading. What’s more, the app advises users to skip submitting a reading if they have consumed alcohol the night before. Or if they feel unwell, or even if they wake up two hours earlier or later than usual.
