The characteristics of infant blood are as follows: 1. Total white blood cell count, the total white blood cell count of newborn infants can reach 25,000/mm3, and then gradually decrease, the normal value is around 10,000-12,000/mm3. 2. Ratio of neutrophils to lymphocytes, the ratio of neutrophils to lymphocytes of newborn infants is high, up to about 70%, and then lymphocytes gradually increase and neutrophils gradually decrease. Then lymphocytes gradually increase and neutrophils gradually decrease. There is a crossover between lymphocytes and neutrophils on the 4th and 6th day after birth, and then lymphocytes gradually increase and leukocytes gradually decrease. 3, hemoglobin characteristics, hemoglobin is relatively high at birth, above 160g/L, and then gradually decreases, and physiological jaundice appears in newborns. After 6-8 weeks of life, hemoglobin decreases can reach below 110g, physiological anemia appears, then gradually rebound, reaching more than 110g 6 months after birth.