Evaluating the Effectiveness of the Dynamic Optimal Timing Fertility Awareness Based Method for Family Planning and Contraception

Objective: Electronic fertility awareness-based methods (FABMs), such as the Dynamic Optimal Timing (DOT) app, are increasingly popular as non-hormonal alternatives for pregnancy prevention. A clinical trial (NCT02833922) evaluating DOT’s effectiveness for pregnancy prevention reported a 1.0% perfect-use and 5.8% typical-use failure rate over 13 cycles. However, these estimates did not explicitly define “use” and how to account for additional methods of use such as withdrawal or condoms. This analysis reevaluates who should qualify as a “user” based on behavior during low-risk days and explores how different inclusion criteria affect failure rate estimates. Our goal is to improve comparability with other FABM research and better evaluate the app's efficacy by dividing participants into behavior-based approaches and implementing behavior-specific censoring restrictions. Methods: We analyzed data from the original DOT trial using a stratified life-table approach among 718 participants across up to 13 menstrual cycles of follow-up. Separate analyses were performed using three different approaches to determine which cycles were included, based on participants’ contraceptive behavior on low-risk days.: (1) those with at least one unprotected sex event, (2) those who only had unprotected sex without any backup methods, and (3) those who used withdrawal or had unprotected sex. Results: Failure rates varied based on a censoring approach. The original study reported a 5.8% failure rate across 5,397 cycles. In our analysis, users who had unprotected sex on low-risk days without any backup methods had a failure rate of 13.4% (836 cycles). Those who used withdrawal or had unprotected sex had a 7.2% failure rate (2,681 cycles), while those with any unprotected sex on low-risk days had a 13.8% failure rate (1,752 cycles). Conclusion: DOT’s effectiveness varies by how users behave on low-risk days as a proxy for use of other contraceptive methods. The original 5.8% typical-use failure rate included all participants who did not meet perfect-use criteria, regardless of how they used other methods of contraception. Restricting analysis and stratifying contraceptive behavior during low-risk days resulted in higher failure rate estimates, ranging from 7.2% to 13.8%. These findings highlight the need for clear user definitions in FABM studies for comparability with existing literature and behavior-based counseling.