Physiological weight loss in newborns refers to the weight loss of newborns within 1 week of birth due to physiological factors. Physiological weight loss can not exceed 10% of birth weight for full-term infants and 15%-20% of birth weight for preterm infants, and can recover to the birth weight in about 10 days of life. The weight recovery rate of preterm infants is slower than that of full-term infants, so parents should enhance feeding and appropriate water intake to ensure the balance of the newborn’s intake and output, and monitor the changes in the child’s weight. If the child’s weight still does not return to the birth weight after more than 10 days, it is necessary to promptly consult a doctor and improve the relevant tests to exclude other diseases that cause the child’s growth retardation.