Normal menstrual flow volume range and its characteristics measured from sanitary napkins in Japanese women: Discrepancy between measured and subjective menstrual flow volume

The 2018 International Federation of Gynecology and Obstetrics abnormal uterine bleeding System-1 defines menstrual flow volume on a 3-point scale based on subjective assessment. However, the normal flow range has not been established, and it is unclear whether subjective assessment is accurate. We investigated the normal menstrual flow volume range in Japanese women and whether the actual measured menstrual flow volume agreed with the subjective evaluation.