Abstract
Background. To investigate natural menstrual bleeding patterns in pre- and perimenopausal women, a prospective observational population study was carried out. Methods. A total of 1616 (80.8%) of a population-based sample of 2000 Danish women aged 45-54 years answered an initial questionnaire. Of 1059 women with natural gynecological functions, 951 (89.8%) completed 1 year of daily recording of bleeding. Of these women, 592 were pre- or perimenopausal and were included in this study. Main outcome measures. Length and heaviness of bleeding episodes, including frequency of spotting, flooding and prolonged bleeding, according to regularity of cycles. Results. The proportion of women with irregular cycles increased from 58.3% at age 45-46 years to 100% at age 53-54 years ( P < 0.001). Irregularity of cycles was accompanied by increased variation in both length and subjective assessment of heaviness of bleeding episodes in the individual woman and between women ( P < 0.001). Episodes of spotting ( P < 0.001) and prolonged bleeding (10 days or more) ( P < 0.001) were more common in women with irregular cycles. Subjective assessment of heaviness of bleeding episodes, however, was higher in women with regular cycles ( P < 0.001). One or more episodes of flooding were recorded by 24.0% of all women irrespective of regularity of cycles ( P = 0.40) but more frequently in younger women ( P < 0.001). Conclusions. Irregularity of cycle lengths at the end of the fertile period is common, and is accompanied by an increased inter- and intraindividual variation in the length and heaviness of bleeding episodes, including increased frequency of prolonged bleeding and spotting.