Women’s Health
Is This My Period? Defining Menses in Epidemiological Research Maegan E. Boutot* Maegan Boutot Brian W. Whitcomb Elizabeth R. Bertone-Johnson
Introduction: Menses length is a reproductive health indicator but has no standard definition. Two often used definitions are from the International Federation of Gynaecology and Obstetrics (FIGO) and the World Health Organization (WHO); the primary difference between them being that FIGO considers one day of low-intensity bleeding (spotting) prior to heavier bleeding as the start of menses. No definition addresses spotting after heavy bleeding, and it is unclear what to do with mid-menses spotting. This ambiguity leave researchers, clinicians, and people with menses at risk for misunderstanding what is “typical” menses length, impacting research and clinical care.
Methods: We applied the WHO, the FIGO and a modified FIGO definitions to menstrual diaries from the Effects of Aspirin in Gestation and Reproduction (EAGeR), a pre-pregnancy cohort with no birth control use. Daily bleeding was recorded as 0 (none), 1 (spotting), or 2-5 (light to heavy flow). We examined how definitions and inclusion of spotting impacted mean, median, and clinical categorization of length into short (3 day), typical (4-8 days), and long cycles (9+ days).
Results: Participants (n=1,039, mean age 28.7 years) contributed 55,078 days with bleeding scores of 0-5. Participants defined 39.3% of any bleeding as spotting; 96.3% of participants reported spotting. WHO and FIGO definitions had similar median (4 days) and mean (about 4.3 days) menses lengths; including post-bleeding spotting days increased the median and mean to greater than 5 days. One in three (36.3%) menses would have different clinical categorizations based on definition, largely due to how spotting following heavier bleeding was categorized.
Discussion: Spotting was commonly reported by EAGeR participants, and meaningfully impacts the distribution of clinical cycle lengths. Additional consideration of spotting is needed to develop definitions for research and clinical care and to investigate associations with clinical outcomes.
