Before 3 months of age, the baby’s weight gain is the most rapid period, about 1kg or more per month; after 3 months, the weight gain slows down rapidly, during the period of 3-6 months, the weight gain is about 0.5kg or more per month; after 6 months, the weight gain decreases further, from 6 to 12 months, the weight gain is about 0.2-0.3kg per month, from 1 to 2 years old, the weight gain is about 2-3kg. Between 1 and 2 years old, the child’s weight increases by about 2-3 kg. After 2 years of age and before puberty, the weight gain is about 1-2 kg per year.