Weight is the most important indicator of physical development and nutritional status of infants and children. The average birth weight of normal newborns in China is 3.20 to 3.30 kg. Most newborns have a physiological weight loss after birth, which reaches its lowest point in 3 to 4 days and can return to the birth weight in about 7 to 10 days, with a maximum weight loss of 200 to 300 grams. Most of the reasons for physiological weight loss are due to the fact that newborn babies cannot immediately adapt to the environment outside the mother’s body, which is characterized by more sleep and less food, insufficient sucking of milk, and evaporation of a lot of water from the lungs and skin, as well as excretion of urine and stool, resulting in weight loss. If the weight loss is too much or does not return to the birth weight in more than 10 days, the cause should be found and analyzed to see if it is due to insufficient breast milk, unreasonable feeding or illness, so that early measures can be taken. 0-1 years old Infants generally gain 0.8~1.5 kg at full term, with an average of 1.0~1.1 kg; the average weight gain in the second and third months after birth is about 1.2 and 1.0 kg; the average weight gain in the fourth to sixth months is 0.45~0.75 kg per month; the average weight gain in the seventh to twelfth months is 0.22~0.37 kg per month, with a total weight gain of about 6.5 kg throughout the year. The growth rate is the fastest in the first 3 months after birth, and then gradually decreases with the growth of monthly age. Generally, the weight of 3 months after birth is about 2 times of the birth weight, and the weight of 1 week old is about 3 times of the birth weight. After the age of 1 year, the growth rate of weight decreases further after the age of 1 year, and they can walk independently and increase their activity. Externally, children after 1 year of age are not as fat as before. This is a normal phenomenon and should not be considered as inadequate nutrition or disease. Generally, the weight gain is about 2.0 to 2.5 kg throughout the year from 1 to 2 years old, and about 2.0 kg throughout the year from 2 to 3 years old, so the weight of a 2-year-old child should be 10 to 12 kg, and the weight of a 3-year-old child should be 12 to 14 kg. The importance of regular weight measurement It is very important for infants and children to have their weight measured regularly. If weight does not increase or decrease as usual, except for illness, it is mostly due to improper care or insufficient nutrition supply, which must be corrected in time. The frequency of weight measurement should be once a month for infants under 6 months of age, preferably once every 2 months from 6 to 12 months, once every 3 months from 1 to 2 years of age, once every 6 months from 3 to 6 years of age, and once a year from 6 years of age. Each time the number is measured, it should be recorded and compared with the standard for normal children. Recognizing weight curves In child health care, growth charts are often used to systematically monitor the physical development of children. Growth charts show the normal growth pattern of children and indicate the normal range of variation, and they are easy to use. How to use the weight chart Find the location of the corresponding weight in the position of the measurement month and draw the point, where it falls within the 25th to 75th percentile is medium, between the 75th to 97th percentile is medium to high, above the 97th percentile is high; between the 3rd to 25th percentile is medium to low, below the 3rd percentile is low. If the infant’s weight is above the 97th percentile or below the 3rd percentile, or if the curve connecting the points traced in several measurements flattens or decreases, the infant should be examined by a doctor so that problems can be detected and corrected in time.