Natural Cycles App: Contraceptive Outcomes and Demographic Analysis of UK Users

Objective: Digital fertility awareness-based contraception offers an alternative choice for women who do not wish to use hormonal methods or are unable to use hormones due to medical reasons. It is also popular among women who may be planning a pregnancy over the coming years and wish to educate themselves about their individual menstrual cycle and fertility. The aim of this study was to investigate the key demographics of current users of the Natural Cycles app and assess the effectiveness of the app at preventing pregnancy for a cohort of women from the United Kingdom. Setting: Users of the Natural Cycles mobile application. Participants: 12,247 women in the UK who used Natural Cycles as their primary method of contraception. Outcome Measures: Cohort demographics and risk of unintended pregnancy. Study Design: Observational prospective real-world cohort study. Results: Users contributed an average of 9.9 months of data for a total of 10,066 woman years of exposure. The mean age of the cohort was 30, mean BMI 23.4, the majority were in a stable relationship (83.2%) and had a university degree or higher (83%). The most common form of contraception used prior to natural cycles was combined oral contraceptive (COC)(39.3%). The one year typical use, PI was 6.1 (95% CI: 5.6, 6.6) and with perfect-use was 2.0 (95% CI: 1.3, 2.8). 13 cycle pregnancy probability was 7.1%. Age was found to be associated with contraceptive outcomes, those between 29-34 had a significantly higher pregnancy probability than those aged 34-45 (8.9% vs 5.0%; p=0.0005). In total 41.9% of users were still using the app at the end of the study. Conclusion: This is the first study which describes the use of a digital contraceptive by women in the UK. It describes the demographics of users and how they correlate with the apps effectiveness at preventing pregnancy. Its findings support previously published effectiveness rates for Natural Cycles in a number of countries.