It’s not often that one has cause to use ‘nuclear physics’, ‘mobile app’ and ‘menstrual cycle’ in one sentence. The three concepts seem wildly disparate. Let’s see what they have to do with each other.

The woman responsible for bringing these concepts together is Elina Berglund, co-founder and chief technical officer of mobile fertility app Natural Cycles. Berlund is a Swedish nuclear physicist who was a member of the team that discovered the Higgs boson at Cern. Berglund co-founded the company with her husband, physicist Raoul Scherwitzl and Natural Cycle’s CEO.

Natural Cycles is the world’s only app that has been certified for use as a contraceptive. The app makes use of a sensitive thermometer and an algorithm that accurately detects and predicts ovulation and fertility. The two founders used their knowledge in advanced mathematics and data analysis to develop the app.

Natural Cycles works by detecting a woman’s ovulation and calculating her fertile days by taking a number of factors into account. All a woman has to do is to take her temperature every morning when she wakes up and enter the reading into the app. An algorithm that accurately detects and predicts ovulation and fertility then tells her via color coding where she is in her menstruation cycle. On red days: be careful or abstain all together, because you can get pregnant. On green days: you’re not fertile, go for it!

The good news is that this digital version of birth control is highly effective. As can be expected of highly qualified scientists, Natural Cycles has completed two clinical trials and more are on the way.

The first study looked at whether Natural Cycles accurately predicts the day of ovulation. The result is a very comforting one for anyone deciding to rely on the app to avoid pregnancy or trying to fall pregnant. The rate at which the algorithm mistakenly marked a day as ‘green’ was less than 0.1%.

The second study analysed the effectiveness of Natural Cycles as a contraceptive. The study showed that the effectiveness of Natural Cycles, when used correctly, is on a par with the pill. Around 4,000 women participated in the clinical trial and only seven out of 100 women who wanted to prevent pregnancy, got pregnant using the app.

Many women around the world want to move away from birth control thatis invasive or messes with their hormones. Natural Cycles is a welcome alternative that has been clinically verified and certified. Tüv Süd, the European inspection and certification organisation, certified Natural Cycles as a class IIb medical device intended for use as a contraception. This puts the app in the same category as the condom, incubators for babies and dialysis devices.

Natural Cycles has over 150,000 users in 161 countries. Of course, the app is only as good as the person using it – for it to be a reliable predictor of ovulation, the user must use it correctly: take temperature every day and avoid unprotected sex on red days.