Introduction: In recent years there has been an explosion in the development of medical apps, with more than 40,000 apps now available. Nearly 100 apps allow women to track their fertility and menstrual cycles and can be used to avoid or achieve pregnancy. Apps offer a convenient way to track fertility biomarkers. However, only some use evidence-based fertility awareness-based methods (FABMs), which with ideal use have rates of effectiveness similar to those of commonly used forms of hormonal birth control. Since having a baby or preventing a pregnancy are important responsibilities, it is critical that women and couples have access to reliable, evidence-based apps that allow them to accurately track their fertility. Methods: We developed a tool to evaluate and rate fertility apps. This tool is specifically designed to help couples avoid pregnancy. Results: Results showed that the majority of fertility apps are not based on evidence-based FABMs or include a disclaimer discouraging use for avoiding pregnancy. However, at least 1 app in each FABM category (except symptohormonal methods) had a perfect score on accuracy. Conclusion: Relying solely on an app to use an FABM, without appropriate training in the method, may not be sufficient to prevent pregnancy.