Digital fertility awareness-based contraception offers an alternative choice for women who do not wish to use hormonal or invasive methods. The aim of this study was to investigate the key demographics of current users of the Natural Cycles app and assess the contraceptive outcomes of women preventing pregnancy in a UK cohort of women.

Materials and Methods

This was a real world observational prospective observational study. The typical-use effectiveness of the method was calculated using both 13-cycle cumulative probability of pregnancy (life table analysis) and Pearl Index for the entire study cohort. Perfect-use PI was calculated using data from cycles where sexual intercourse during the fertile window was marked as protected and no unprotected sex was recorded on fertile days.


12,247 women were included in the study and 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 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%.


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.


目的:基于数字生育意识的避孕方法为不希望采用激素或侵入性方法的女性提供了另一种选择。本研究的目的是调查目前自然周期app用户的主要人口统计学特征, 并评估英国女性队列中计划避孕女性的避孕效果。

材料与方法:这是一项真实世界的观察性前瞻性研究。在整个研究队列中, 采用13个周期的累积怀孕率(生命表分析)和Pearl指数(PI)来计算该方法的典型采用效果。完美采用PI是采用来自周期的数据计算的, 其中在生育窗口期的性交被标记为被保护的, 而在受孕的日子里没有记录无保护的性行为。

结果:12247名女性参与了这项研究, 她们平均贡献了9.9个月的数据, 总共暴露了10066女性年。队列的平均年龄为30岁, 平均体重指数为23.4, 大多数人关系稳定(83.2%), 拥有大学或以上学历(83%)。典型采用1年的PI为6.1(95%CI:5.6, 6.6), 良好采用的PI为2.0(95%CI:1.3, 2.8)。13个周期妊娠率为7.1%。

结论:这是第一项描述英国女性采用数字避孕的研究。它描述了用户的人口统计数据, 以及她们与app在避孕方面的有效性之间如何关联。



We wish to thank James Trussell for his input and support which contributed greatly to the methodological foundations from which this manuscript was created and Federiko Barabas for his contributions to data analysis.

Disclosure statement

Conflict of interest: E.B.S. and R.S. are the scientists behind the application Natural Cycles and the founders of the company with stock ownership. J.T.P, E.M., F.B.,M.Ch and S.R. are employed by Natural Cycles Nordic AB. H.K.K and K.G.D. serve on the medical advisory board of Natural Cycles and has received honorarium for participating in advisory boards and/or giving presentations for matters related to contraception and fertility regulation for Ferring (K.G.D), Exelgyn (K.G.D) and Mithra (K.G.D). SW provides consultancy services to Natural Cycles and has received honoraria for attending meetings and giving presentations for matters related to technology, fertility awareness and contraception.

Ethics approval and consent to participate

The study protocol was reviewed and approved by the regional ethics committee (Etikprovingsmyndigheten (EPN), Stockholm, diary number 2017/563-31). Users of the Natural Cycles app consent for use of their anonymised data for research when signing up. They can withdraw consent at any time within the app. This is a digitised form of written consent. The EPN reviewed and approved this digitised procedure for obtaining informed consent.

Consent to publish

All authors consent for the publication of the research article content.

Author contributions

E.M. and S.R. planned and designed the study. M.Ch performed acquisition and analysis of data under supervision of E.B. J.T.P., M.Ch.,E.M., and S.R. interpreted the study data and JTP wrote the manuscript. S.W., KGD., R.S., and E.B.S critically reviewed the manuscript and approved the final version for submission. All authors have read and approved the manuscript.

Data availability statement

The datasets generated and/or analysed during this study are not publicly available due to the proprietary nature of the algorithm and complexity of outputs but are available from the corresponding author on reasonable request.

Additional information


The study was funded by Natural Cycles Nordic AB. The role of the funder was that paid employees of Natural Cycles analysed the user data and made results available for interpretation by authors.

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