growth charts are used to assess a child's growth over time, so that an overall pattern in development can be seen and any problems highlighted (e.g. obesity, malnutrition, dwarfism)
a baby's growth is monitored regularly after birth to make sure it's growing normally. the three measurements taken are: length, mass and headcircumference
the results taken are plotted on growth charts
charts show a number of percentiles (e.g. the 50th percentiles shows the mass that 50% of babies will have reached at a certain age)
babies vary in size, by doctors are likely to investigate if a baby's size is above the top percentile line or below the bottom percentile line, their size increases or decreases by 2 or more percentile lines, or if there's an inconsistent pattern