Growth charts have long been a passion of mine. It's the math geek in me coming out. I love to plot data and see trends and help parents understand what is normal. Normal is a relative term. What is normal for one baby is not normal necessarily normal for another.
Given this proclivity, I have a scale in my office and record weights at almost every visit. A major requirement of my EHR was that it had to use the WHO Growth Charts. An aside about the WHO Growth Charts - these are charts that are based on breastfed babies around the world. The data was collected at specific times in their growth over a 2 year period. This data does not include babies fed formula, who were premature, who had a mother who smoked, and several other criteria. These charts are about what is normal for a baby who is exclusively fed breastmilk until 6 months and then introduced culturally appropriate foods.