Natural Cycles is an algorithm-based digital contraceptive tool, the first of its kind to receive FDA approval . Numerous reports of unexpected pregnancies among users, however, have raised questions about the role of technologies like this one in driving important personal health decisions.
The app is built on an algorithm that leverages a user’s self-reported basil body temperature and period cycle days to predict when the user is ovulating, improving the reliability of its predictions over a learning term of few cycles . The app pinpoints a user’s fertile days with a high degree of precision , signaling to the user with a color-coded screen whether having sex on a given day has the potential to result in pregnancy or not. Developed in Sweden by Co-Founder Dr. Elina Berglund, a former particle physicist at CERN, the algorithm is designed to account for uncertainties like sickness and alcohol consumption as it customizes the probability of conceiving for each unique user .
Clinical studies have shown that Natural Cycles has a “perfect use” failure rate of 1% and a “typical use” failure rate of 6.8% . Compared to the most commonly used methods of contraception like hormonal birth control pills, IUDs, and condoms, Natural Cycle’s offers a similar failure rate without the discomfort of taking hormone-based contraceptives or relying on condoms . Fundamentally, Natural Cycles has improved upon the age old “rhythm method” by replacing burdensome tracking with a digital app and a smart algorithm. As critics readily point out, it has not, however, been able to correct for human inaccuracies in gathering and reporting data .
After a hospital in Stockholm reported in early 2018 that 37 out of 668 requested abortions since September had been users reliant on Natural Cycles , public skepticism took over headlines about the company. Natural Cycles spokespeople responded: “no contraception is 100 percent effective, and unwanted pregnancies are an unfortunate risk with any contraception” . A recently completed review by Swedish investigators confirmed this assertion .
At the request of Swedish regulators, Natural Cycles is responding to the crisis by clarifying the risks associated with using the product . The UK’s Advertising Standards Authority has similarly warned that the company’s 99% “perfect use” accuracy claim is going too far . Natural Cycles is thus changing its claims to focus on the 93% accuracy for “typical use”, recognizing the role human reporting plays in driving the bulk of the variation in the algorithm’s efficacy .
In the longer term, Natural Cycles plans to focus on comparative trials that assess the efficacy of the product in relation to traditional methods of birth control . However, with several years needed to carry out these studies, the intermediate priority is product development and international expansion . This starts with additional research into women’s health and markers of fertility, both of which could lead to an improved algorithm and potential adjacent products .
As Natural Cycles continues to grow, it should focus on two key opportunities:
- Short Term: Build closer relationships with physicians to build a network of advocates for the product
- Medium Term: Invest in a wearable that can automatically gather a user’s data, thereby limiting the risk of reporting error
Building greater buy-in with physicians and the medical community is essential to managing the downside risk of recent media coverage. Scathing comments from doctors about the role of human error in this product are persistent throughout coverage, despite the product having a “typical use” failure rate similar to that of traditional birth control. As the rollout of autonomous vehicles has shown, the public expects products built on machine learning to have a “typical use” failure rate closer to 0%, a much higher standard than human-led precedents. Building more support among doctors could help change public perception as well as create an organic future promotion channel for the app.
In the medium term, Natural Cycles can invest in a wearable that automatically gathers a user’s temperature as well as other relevant indicators like pulse rate. Companies like Zurich-based Ava are already pioneering wearables that do exactly this, successfully gathering a wider range of data to predict a user’s fertility . This is essential to reducing the “typical use” failure rate to a level closer to the “perfect use” rate. Doing so could place Natural Cycles clearly ahead of hormonal birth control and condoms as a method of contraception. Can an algorithm replace the pill? I’d bet on it.
As we think about this product and future ones like it, should machine learning-based digital health products have a higher standard for efficacy in order to be approved by the FDA? Or should we treat this the same way we treat existing contraceptives?
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 “FDA allows marketing of first direct-to-consumer app for contraceptive use to prevent pregnancy,” FDA press release (August 10, 2018).
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 Alexandra Sifferlin, “Can an App Prevent Pregnancy?” TIME, August 15, 2018, http://time.com/5365564/fertility-apps-contraception/, accessed November 2018.
 Natasha Lomas, “Natural Cycles Contraception App Told to Clarify Pregnancy Risks,” TechCrunch, September 17, 2018, https://techcrunch.com/2018/09/17/natural-cycles-contraception-app-told-to-clarify-pregnancy-risks/, accessed November 2018.
 Mohaned Shilaih, Valérie de Clerck, Lisa Falco, Florian Kübler & Brigitte Leeners, “Pulse Rate Measurement During Sleep Using Wearable Sensors, and its Correlation with the Menstrual Cycle Phases, A Prospective Observational Study,” Scientific Reports, no. 7 (May 2, 2017): 1294, via Nature.com, accessed November 2018.
 Daniel Winkler, “As More Women Choose to Have Babies Later, a Fertility Fitbit May Help,” NBC News, September 26, 2016, https://www.nbcnews.com/mach/technology/fertility-fitbit-more-women-choose-have-babies-later-life-n654411, accessed November 2018.
[Title Image Citation] Berenice Magistretti, “Natural Cycles is First Contraceptive App to get EU Approval,” VentureBeat, February 9, 2017, https://venturebeat.com/2017/02/09/natural-cycles-is-first-contraceptive-app-to-get-eu-approval/, accessed November 2018.