Assessment of menstrual regularity and irregularity using self-reports and objective criteria.

To assess subjective and objective definitions of menstrual regularity, and the relationship between them, 114 university students (mean age 20.3 years) prospectively recorded eight consecutive menstrual dates and reported whether they considered themselves 'regular' or 'irregular'. The percentage of women who reported being menstrually 'regular' or menstrually 'irregular' was compared with a classification developed according to a criterion based upon the results of their prospective menstrual records. According to self-reports and objective measures of regularity, a similar portion of the women (about 70%) were regular. But when cross-classifying regularity and non-regularity by the two procedures, it was found that only 44% of those who defined themselves as irregular were likewise defined by the objective criteria, whereas 82% of the women who defined themselves as regular were also deemed so by the objective criteria. It is concluded that some women will, and others will not, construe 'variability' as 'irregularity'.