title: Bleeding after use of the levonorgestrel regimen of emergency contraception: concordance between women's reports of their menstrual periods and an objective algorithm.
abstract: OBJECTIVE
  To compare concordance between periods as recorded by women on daily diaries with those determined objectively by an algorithm used in an earlier study to assess bleeding patterns after taking the emergency contraceptive pill (ECP) regimen consisting of 1.5 mg levonorgestrel.
  
  
  METHODS
  We asked 120 women who had been treated with the regimen to keep daily bleeding diaries for 9 weeks. We compared menstrual periods recorded on the diary cards and reported in follow-up interviews with those determined by an algorithm adapted from the World Health Organization (WHO).
  
  
  RESULTS
  Altogether, 111 subjects contributed diary cards on which the algorithm could identify at least one period; a total of 261 periods were identified by the algorithm. In 87% of these periods, women recorded on the diary a start date that was the same as or only 1 day later, but in 8% their recorded start day was more than 7 days later. For the first period following use of the regimen, concordance was lower: 81% and 14%, respectively.
  
  
  CONCLUSIONS
  We found generally good concordance between the starts of menstrual periods as determined by an algorithm adapted from the WHO and the date of the start of a period as reported by participants on diary cards. In our earlier study, we found that the earlier in the cycle a woman took 1.5 mg levonorgestrel, the earlier was the next period. Had we relied on women's recording of the first period on the diary card, we would not have reached that conclusion.
authors.affiliation: Office of Population Research, Princeton University, Princeton, NJ 08544, USA. trussell@princeton.edu
authors.forename: James
authors.initials: J
authors.lastname: Trussell
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D044363:Contraception, Postcoital / Q000009:adverse effects / Q000379:methods*; D003271:Contraceptive Agents, Female / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D016912:Levonorgestrel / Q000009:adverse effects / Q000627:therapeutic use*; D008597:Menstrual Cycle / Q000187:drug effects*; D008796:Metrorrhagia / Q000139:chemically induced / Q000453:epidemiology*; D013997:Time Factors
chemical_list: D003271:Contraceptive Agents, Female; D016912:Levonorgestrel