There are 2 sets for the WHO growth chart. According to the website “Canadian Paediatric Endocrine Group – WHO Growth Charts for Canada”: Set 1: uses percentile lines at 3 / 15 / 50 / 85 / 97 (and in some charts, 99.9) for all ages. Canadian Pediatric Endocrine Group+1 Set 2: uses percentile lines at 3 / 10 / 25 / 50 / 75 / 90 / 97 (and retains 99.9 in some charts) for all ages. Canadian Pediatric Endocrine Group+1 We have to use Set 2: More percentile lines provide greater granularity. That means we can detect smaller shifts in growth trajectory (for example, a child moving from ~75th percentile to ~50th percentile) more easily, rather than only broadly seeing “below 85th” or “above 50th”. The CPEG notes that Set 2 “increased granularity … will allow these charts to be more easily applied to identify growth aberrations The percentile cut-offs used in Set 2 are more familiar to many clinicians (because they resemble the percentiles used in the Centers for Disease Control and Prevention (CDC) charts) and thus are easier to interpret in practice. Some of the older chart formats (Set 1 or earlier) lacked intermediate lines and had very few percentile bands between 3rd and 97th. That made it harder to notice when a child was “crossing centiles” or showing a subtle change in growth trajectory. For reference: https://cpeg-gcep.net/content/who-growth-charts-canada Regards Nicole