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      Typical use effectiveness of Natural Cycles: postmarket surveillance study investigating the impact of previous contraceptive choice on the risk of unintended pregnancy

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          Abstract

          Objective

          To investigate the association between contraceptive effectiveness of Natural Cycles and users’ previous choice of contraceptive, and to evaluate the impact of shifting from other methods to Natural Cycles on the risk of unintended pregnancy.

          Setting

          Natural Cycles mobile application.

          Participants

          16 331 Natural Cycles users in Sweden for the prevention of pregnancy.

          Outcome measures

          Risk of unintended pregnancy.

          Study design

          Real world evidence was collected from Natural Cycles users regarding contraceptive use prior to using Natural Cycles and sexual activity while using Natural Cycles. We calculated the typical use 1-year Pearl Index (PI) and 13-cycle failure rate of Natural Cycles for each cohort. The PI was compared with the population PI of their stated previous methods.

          Results

          For women who had used condoms before, the PI of Natural Cycles was the lowest at 3.5±0.5. For women who had used the pill before, the PI of Natural Cycles was the highest at 8.1±0.6. The frequency of unprotected sex on fertile days partially explained some of the observed variation in PI between cohorts. 89% of users switched to Natural Cycles from methods with higher or similar reported PIs.

          Conclusion

          The effectiveness of Natural Cycles is influenced by previous contraceptive choice and this should be considered when evaluating the suitability of the method for the individual. We estimate that Natural Cycles usage can reduce the overall likelihood of having an unintended pregnancy by shifting usage from less effective methods.

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          Most cited references7

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          Contraceptive failure in the United States.

          This review provides an update of previous estimates of first-year probabilities of contraceptive failure for all methods of contraception available in the United States. Estimates are provided of probabilities of failure during typical use (which includes both incorrect and inconsistent use) and during perfect use (correct and consistent use). The difference between these two probabilities reveals the consequences of imperfect use; it depends both on how unforgiving of imperfect use a method is and on how hard it is to use that method perfectly. These revisions reflect new research on contraceptive failure both during perfect use and during typical use. Copyright © 2011 Elsevier Inc. All rights reserved.
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            Identification and prediction of the fertile window using NaturalCycles.

            The aim of the study was to evaluate the ability of a novel web and mobile application to identify a woman's ovulation day and fertile window, in order to use it as a method of natural birth control.
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              Fertility awareness-based mobile application for contraception

              Abstract Objectives: The aim of the study was to retrospectively evaluate the effectiveness of a fertility awareness-based method supported by a mobile-based application to prevent unwanted pregnancies as a method of natural birth control. Methods: In a retrospective analysis, the application’s efficiency as a contraceptive method was examined on data from 4054 women who used the application as contraception for a total of 2085 woman-years. Results: The number of identified unplanned pregnancies was 143 during 2053 woman-years, giving a Pearl Index of 7.0 for typical use. Ten of the pregnancies were due to the application falsely attributing a safe day within the fertile window, producing a perfect-use Pearl Index of 0.5. Calculating the cumulative pregnancy probability by life-table analysis resulted in a pregnancy rate of 7.5% per year (95% confidence interval 5.9%, 9.1% per year). Conclusions: The application appears to improve the effectiveness of fertility awareness-based methods and can be used to prevent pregnancies if couples consistently protect themselves on fertile days.
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                Author and article information

                Journal
                BMJ Open
                BMJ Open
                bmjopen
                bmjopen
                BMJ Open
                BMJ Publishing Group (BMA House, Tavistock Square, London, WC1H 9JR )
                2044-6055
                2019
                23 March 2019
                : 9
                : 3
                : e026474
                Affiliations
                [1 ] departmentDepartment of Medical Communications , Natural Cycles Nordic AB , Stockholm, Sweden
                [2 ] departmentDepartment of Women’s and Children’s Health , Karolinska Universitetssjukhuset , Stockholm, Sweden
                [3 ] departmentOffice of Population Research , Princeton University , Princeton, New Jersey, USA
                Author notes
                [Correspondence to ] Dr Raoul Scherwitzl; raoul.scherwitzl@ 123456naturalcycles.com
                Author information
                http://orcid.org/0000-0001-9992-3769
                Article
                bmjopen-2018-026474
                10.1136/bmjopen-2018-026474
                6475236
                30904873
                25c38270-3fe0-4c2f-a731-1e6aa969e083
                © Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

                This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

                History
                : 06 September 2018
                : 14 January 2019
                : 13 February 2019
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/100009633, Eunice Kennedy Shriver National Institute of Child Health and Human Development;
                Categories
                Obstetrics and Gynaecology
                Research
                1506
                Custom metadata
                unlocked

                Medicine
                contraception,fertility app,family planning,fertility awareness,information technology,telemedicine

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