A newborn’s daily weight gain is about 30 grams per day because children grow most rapidly during the neonatal period. Most children are twice as heavy as they were at birth during the first three months of life, i.e., they double their birth weight. For example, if a child weighs 3,000 grams at birth, he or she will weigh about 6,000 grams in the first three months of life. Therefore, when parents judge the child’s weight gain, if the child’s weight is less than 800 grams per month, i.e., the child’s weight gain is less than about 20 g per day. At this time, the child’s weight growth is relatively slow, parents should promptly detect the specific reasons for the child. For example, the amount of milk eaten is low, or the child has chronic diarrhea and other reasons.