1. Height and weight development standards 1. What is the average height and weight of a 17-month-old baby? According to data released by the World Health Organization (WHO), the average height of 7-month-old babies is 68.5 centimeters, and there is not much difference between male and female babies. The average weight is about 8.4 kilograms, and there is not much difference between male and female babies. 1.2 How fast does the baby’s height and weight grow? In the first 6 months, your baby’s height and weight increase