how many people are bleeding from menstruation on any given day?
If participants reported any menstrual bleeding on a given day, they were instructed to complete a detailed follow-up menstrual flow questionnaire consisting of the pictograms shown in Figure 1 adapted from Wyatt et al. (27) (without the scales). For each bleeding day, women reported the quantity, size, and observed amount of blood loss for each feminine product used (sanitary napkins or tampons), as well as any extraneous blood loss not captured by sanitary protection. The amount of menstrual blood flow (total blood loss in mL) on each day of bleeding was estimated by using the scales shown in Figure 1, by summing the scores of each sanitary napkin or tampon used on each day. About 15% of reported bleeding days did not have a recorded menses volume in the daily diaries and were marked as missing. If a woman was missing information about either the size or number of sanitary napkins or tampons used for any reported bleeding days, then her total menstrual blood flow was not estimated and was set to missing. These pictograms represent a valid marker for estimating the amount of menstrual blood flow and are highly correlated with blood loss estimates obtained by using the alkaline hematin method (27).
Assessment of menstrual blood loss by pictograms with blood loss equivalents. Adapted from Wyatt KM, Dimmock PW, Walker TJ, et al. Determination of total menstrual blood loss. Fertil Steril. 2001;76(1):125131 (27).
Bleeding amount was measured per day and per cycle for each woman in the study. Cycle blood flow was classified in tertiles as light (?36.5 mL), medium (>36.5 and ?72.5 mL), or heavy (>72.5 mL). Individual bleeding days were classified in tertiles as light (?4 mL), medium (>4 and ?14 mL), or heavy (>14 mL) blood flow. We compared the number of light, medium, heavy, and total bleeding days per cycle, as well as the amounts of bleeding on each calendar day of the cycle.