1. Weight and height development standards 1.1 Weight and development standards According to data from the World Health Organization (WHO), the average weight of a one-year-old baby is 8.7 kilograms, and there is not much difference in the average weight of male and female babies. However, it should be noted that the growth rate and development of each baby are different, so you cannot rely too much on standard values and ignore individual differences. 1.2