As soon as a newborn is born, the doctor will measure the weight of the newborn. Through the measurement, parents can know whether their baby’s weight is normal or not, and the standard range of normal weight is 2500-4000 grams. Usually, the weight of a newborn has a lot to do with the mother’s physical fitness and the level of life and health care during pregnancy, as well as the absorption of nutrients. The latest statistics show that the average weight of newborns has reached 3500 grams, and there is a trend of continued growth. The weight gain after birth should be a continuation of the fetal weight growth in the womb. Within a week after birth due to insufficient milk intake, combined with water loss and meconium discharge, temporary weight loss or physiological weight loss can occur, about 3 to 4 days after birth to reach the lowest point, the range of decline is 3% to 9%, and then gradually rebound, to the 7th to 10th day after birth should be restored to the weight at birth. If the weight loss exceeds 10% or does not return to the birth weight by the 10th day, it is pathological and the cause should be analyzed. If timely and reasonable feeding after birth can reduce or avoid the occurrence of physiological weight loss. After recovering to birth weight, it can increase by 10-15g/Kg per day. 700-1200g can be increased at the end of neonatal period, and the maximum is not more than 1500g.