title: Fertility awareness-based mobile application for contraception.
abstract: OBJECTIVE
  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.
authors.affiliation: a NaturalCycles Nordic AB , Stockholm , Sweden ;
authors.forename: Elina
authors.initials: E
authors.lastname: Berglund Scherwitzl
authors.affiliation: b Division of Obstetrics and Gynecology , Karolinska Institutet and University Hospital , Stockholm , Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Gemzell Danielsson
authors.affiliation: a NaturalCycles Nordic AB , Stockholm , Sweden ;
authors.forename: Jonas A
authors.initials: JA
authors.lastname: Sellberg
authors.affiliation: a NaturalCycles Nordic AB , Stockholm , Sweden ;
authors.forename: Raoul
authors.initials: R
authors.lastname: Scherwitzl
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D015992:Body Mass Index; D001831:Body Temperature; D003267:Contraception / Q000379:methods*; D003268:Contraception Behavior / Q000706:statistics & numerical data*; D005260:Female; D005298:Fertility; D006801:Humans; D015993:Life Tables; D008875:Middle Aged; D063731:Mobile Applications / Q000592:standards; D010061:Ovulation Detection / Q000379:methods* / Q000592:standards; D011247:Pregnancy; D018873:Pregnancy Rate; D011275:Pregnancy, Unwanted; D012189:Retrospective Studies; D011795:Surveys and Questionnaires; D013548:Sweden; D055815:Young Adult
keywords: Basal body temperature method; birth control; menstrual cycle; natural family planning methods; ovulation detection; pregnancy rate; retrospective study