The royal jd chart is a tool that is used to track the growth and development of babies and toddlers. It is named after the Royal Jubilee Maternity Hospital in Belfast, where it was first introduced. The chart is used to plot the weight, length, and head circumference of a child, and it is a crucial tool for healthcare professionals to monitor a child's growth and detect any potential problems early on. The chart is divided into different percentile lines, with the 50th percentile being the average for a child's age and gender. If a child falls below the 5th percentile or above the 95th percentile, it may indicate a potential issue with their growth.