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Practice Clinical Updates

Fertility awareness based methods for pregnancy prevention

BMJ 2019; 366 doi: (Published 11 July 2019) Cite this as: BMJ 2019;366:l4245

Rapid Response:

Re: Fertility awareness based methods for pregnancy prevention

Urrutia & Polis summarise the evidence for use of a range of fertility awareness based techniques for prevention of pregnancy and attempt to provide guidance for clinicians on suitable educational resources to develop skills in counselling techniques. The level of public interest in fertility tracking apps is a clear sign that there is a significant interest in this subject amongst the general public and they should be commended for their work on communicating the key aspects of these techniques.

The effectiveness estimates presented in this review are based on the authors’ own systematic review published in August of 2018, which had cut-off point of June 2017 for inclusion of data. Since June 2017 a significant volume of data has emerged, arguably of high quality, investigating contraceptive outcomes using digital or app-based fertility awareness methods (Natural Cycles and the DOT app) in a total of 23,503 women.1,2 Indeed the data published since the cut-off point of this review is so substantial that it has formed the basis for FDA clearance of one of these apps as a method of contraception. Whilst we acknowledge the need for more research within this space, readers should be aware that the evidence investigating the effectiveness of fertility awareness based methods of contraception goes beyond the data presented within this update article.

Comparison of estimates of effectiveness of different fertility awareness based methods of contraception is challenging and should consider both method dependent and user dependent factors. Digital technologies that facilitate daily tracking and automated analysis of physiological parameters have undoubtedly improved the accuracy of identification of fertile days. The primary reason for failure of digital fertility awareness methods in pregnancy prevention is failure of the user to follow the guidance to avoid unprotected sex.3 User related factors such as lifestyle, willingness of partner to use condoms, motivation to avoid pregnancy are important influencers of effectiveness. When counselling on the effectiveness of different fertility awareness based methods clinicians should be mindful that user experience is likely to have significant impact on compliance levels and therefore effectiveness outcomes.

1. Berglund Scherwitzl, E. et al. Perfect-use and typical-use Pearl Index of a contraceptive mobile app. Contraception (2017). doi:10.1016/j.contraception.2017.08.014
2. Jennings, V., Haile, L. T., Simmons, R. G., Spieler, J. & Shattuck, D. Perfect- and typical-use effectiveness of the Dot fertility app over 13 cycles: results from a prospective contraceptive effectiveness trial. Eur. J. Contracept. Reprod. Heal. Care 1–6 (2019). doi:10.1080/13625187.2019.1581164
3. Bull, J. et al. Typical use effectiveness of Natural Cycles: postmarket surveillance study investigating the impact of previous contraceptive choice on the risk of unintended pregnancy. BMJ Open 9, e026474–e026474 (2019).

Competing interests: No competing interests

16 July 2019
Raoul Scherwitzl
CEO Natural Cycles
Simon P Rowland, Victoria Jennings, Elina Berglund Scherwitzl, Jack Pearson, Kristina Gemzell Danielsson
Natural Cycles Nordic AB
Luntmakargatan 26, 111 37 Stockholm, Sweden