A variety of methods to evaluate bleeding profiles are available. The World Health Organization (WHO) published recommendations for methods of collection and analysis of bleeding patterns. The WHO method includes data collection on bleeding days (days when blood loss requires the use of a menstrual pad or tampon) and spotting days (when no protection was needed) using 90-day referent periods. A second tool, the pictorial blood loss assessment chart (PBAC) has been shown to be an inexpensive and objective method of assessing blood loss. The PBAC takes into consideration how heavy blood flow is as well as the number of sanitary napkins and tampons used. Additionally, new technologies (including mobile period tracking applications) have made retrospective collection of bleeding data more feasible and prospective data collection more accurate.