Normal full-term newborns will experience physiological weight loss after birth, and their weight will be less than their birth weight, and the weight loss will be less than 10% of their birth weight, and their birth weight will be restored in about 10 days, and their weight will gradually increase after 10 days. The physiological weight loss in preterm infants will take a little longer and will return to birth weight in about 2 weeks. After regaining birth weight, the daily weight gain is usually 20-30g, and the urine output should be at least 6 times per 24 hours, indicating that the feeding is proper. If the newborn’s weight loss is greater than 10% of the birth weight, or if there is no weight gain after 2 weeks, it is recommended to consult a doctor promptly. Common causes of weight failure include improper feeding and hypothyroidism, which need to be given sufficient attention.