The Performance of Fertility Awareness-based Method Apps Marketed to Avoid Pregnancy

• Biomarkers
• Birth Rate
• Contraception
• Female
• Fertility
• Menstrual Cycle
• Natural Family Planning
• Pregnancy

The field of women's health and fertility tracking applications (apps) has recently exploded, with nearly 100 apps available to help women track their cycle.¹ The most popular apps have been downloaded over 1 million times each, and up to 60% of women express interest in using natural or fertility awareness-based methods (FABMs) to prevent pregnancy.² These methods are attractive because they lack medical side effects, are effective, and can empower women with knowledge about their bodies. For each evidence-based method (Billings, Creighton, two-day, symptothermal, symptohormonal, standard days, and lactational amenorrhea methods), there are Strength of Recommendation Taxonomy level 1 studies that demonstrate that these methods, when used correctly, have rates of effectiveness similar to those of commonly used forms of hormonal birth control.^3⇓⇓–6

The effectiveness of FABMs depends on women observing and recording fertility biomarkers and following evidence-based guidelines. Apps offer a convenient way to track fertility biomarkers, but only some use evidence-based FABMs.² Until now there have been no objective assessments of the apps designed for use to avoid pregnancy.¹ In this study we developed a rating tool with specific criteria to quantify an app's response to real cycle data based on the clinical guidelines evaluated in level 1 studies.

Methods

We identified 95 apps for study via iTunes, Google, and Google Play searches. Of those, we excluded 55 apps because they either had a disclaimer prohibiting use for avoiding pregnancy or did not claim to use an evidence-based FABM as described in Manhart et al.³

The rating system was developed based on criteria used by Family Practice Management to evaluate medical apps.⁷ We rated each app for 10 clearly defined criteria (each on a 5-point scale), which were weighted based on their level of importance for avoiding pregnancy (Table 1).

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Table 1.

Criteria for Rating Apps

A standardized data set of 7 cycles of daily fertility observations, derived from real cycle data, was used to determine the apps' accuracy in identifying potential days of fertility. For each cycle, evidence-based fertile days (FDs) were determined by applying specific guidelines for each FABM, as evaluated in peer-reviewed studies.³ The accuracy of each app was determined by comparing evidence-based FDs to the fertile days of each cycle as identified by the app, called the app-defined FDs (Figure 1).

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Figure 1.

A comparison of evidence-based fertile days (FDs) and app-defined FDs.

Apps that did not predict fertile days scored high on accuracy only if they recommended prior FABM training apart from the app.

• Received for publication January 16, 2016.
• Revision received March 23, 2016.
• Accepted for publication March 29, 2016.