Premature anemia is defined as anemia that occurs in immature or low birth weight infants within the first year of life. Its incidence is higher than that of full-term infants, and it appears earlier and lasts longer than that of full-term infants. If not taken seriously, it can directly affect the growth and development of preterm infants and cause other complications on this basis, so attention should be paid to prevention and treatment. 1. Classification 1. Early anemia: 4-8 weeks after birth, the life span of red blood cells is shortened, bone marrow hematopoiesis is inhibited, and blood volume increases. 2.Mid-term anemia: 8-16 weeks after birth, bone marrow hematopoiesis starts and blood volume increases. 3.Late stage anemia: after 16 weeks after birth, bone marrow hematopoiesis is active and iron stores are depleted (iron deficiency). 4.Megaloblastic anemia: 6-8 weeks of folic acid deficiency. 5. Hemolytic anemia: 6-10 weeks VitE deficiency. Premature infants with terminal blood Hb 145-121g/L within 3-6 weeks after birth are mildly anemic, 120-100g/L are moderately anemic, and less than 100g/L are severely anemic. Etiology includes physiological factors, nutritional factors, hospital-acquired anemia, medical and surgical diseases, improper artificial feeding, etc. 1. Physiological factors: (1) After birth, newborns establish pulmonary respiration, the oxygen saturation (SaO2) increases rapidly to 95%, and the oxygen release from hemoglobin (Hb) greatly exceeds the oxygen requirement of tissues, thus the bone marrow erythropoietic function is temporarily suppressed, so that early anemia occurs in 4-8 weeks, also called “physiological anemia”. This is also called “physiological anemia”. Physiologic anemia” is a common phenomenon in preterm infants. All preterm infants have a rapid decline in hemoglobin within a short period of time after birth, reaching a minimum value at 4-8 weeks after birth. Some preterm infants with anemia often show clinical signs of tissue hypoxia, such as apathy, difficulty in eating, and serious impact on the growth and development of preterm infants. Therefore, some scholars dispute the claim that preterm infants are “physiologically anemic”. (2) The life span of erythrocytes in preterm infants is shorter than that of term infants, 60-80 days (80-100 days in term infants), which may be due to the relatively large cytosol of their erythrocytes, the stiffness of the cytosolic membrane, the poor compliance of the microvasculature, and the shorter half-life of their HbF compared to HbA. (3) Rapid growth and development. In the first few weeks after birth, especially in preterm infants, the growth rate is faster and the blood volume increases rapidly with the increase in body weight, while the hematopoietic function of bone marrow is relatively insufficient at this time. (4) Low erythropoietin (EPO) activity and lack of erythropoietin stimulation in the bone marrow reduce the differentiation and maturation of erythrocytes. During preterm infants’ anemia, the increase in blood EPO concentration is significantly lower than that recognized in children with the same level of anemia, and the younger the gestational age, the lower the EPO concentration. The correlation between the rise in blood EPO and the fall in Hb is poor in preterm infants, and the response of EPO to tissue hypoxia is significantly lower than in adults. 2. The effect of gestational age and weight on anemia in preterm infants The younger the gestational age, the earlier the appearance of anemia and the more severe it is. It may be related to the following aspects: preterm infants gain weight quickly and their blood volume increases rapidly with their weight, while the hematopoietic function of bone marrow is relatively insufficient at this time, resulting in blood dilution; preterm infants have less iron stores than full-term infants, and the lower their weight, the less iron stores they have; preterm infants have increased erythropoietin since 6 weeks after birth or during erythropoietin treatment, which accelerates erythropoiesis and increases iron consumption. 3. Nutritional factors are generally considered to play an important role in the anemia that occurs in late preterm infants. Among them, iron, vitamin E and folic acid are the main ones, especially the first two are more important. (1) Iron: Iron plays an important role in the anemia of preterm infants. The fetus maintains a constant level of iron throughout pregnancy. Iron in the body exists in three forms, namely hemoglobin iron, tissue iron and stored iron, 75% of which is stored in Hb. Preterm infants have low iron stores and develop iron deficiency earlier than full-term infants. Although the Hb level is normal at birth, if the preterm infant is not supplemented with iron for 2 months after birth, the stored iron will be exhausted when the body weight is multiplied. Therefore, it is best to supplement iron within 2 months after birth to avoid late anemia. (2) Vitamin E: It is an antioxidant necessary to keep red blood cells intact. The smaller the birth weight of the baby, the more severe the deficiency. (3) Folic acid: The active form of folic acid (tetrahydrofolate) is involved in the synthesis of deoxyribonucleic acid (DNA) and can cause megaloblastic anemia when deficient in folic acid. Although the folic acid content in serum serum and red blood cells of postnatal infants is high, it decreases sharply within 2-3 weeks, and decreases even more in low birth weight infants, and is at its lowest level 1-3 months after birth. 4. Blood loss: fetal-placental blood transfusion, medical blood loss. Clinical manifestations 1.In addition to slightly pale face and nails, there are generally no obvious symptoms and signs. 2. In more severe anemia, persistent tachycardia (160 beats/min), shortness of breath (50 breaths/min) without intrapulmonary disease, and sometimes apnea suggesting symptoms of hypoxia may occur. Difficulty in breastfeeding, indifferent expression, easy fatigue, and slowed weight gain. 3. 4-10 weeks after birth if accompanied by vitamin E deficiency can cause absurdity due to hemolytic anemia, crying and restlessness, a few appearing eyelids, lower limbs, feet, scrotum edema, etc. Laboratory tests 1. Hb: the newborn has venous blood HbQ130g/L within 1 week after birth, capillary HbQ145g/L, Hb <100g/L after one week after birth, can be diagnosed as anemia; physiological anemia is positive cellular positive pigment anemia. Reticulocytes were normal. The lowest value of hemoglobin in physiological anemia of preterm infants can be 65-90 g/L. In case of hemolytic anemia caused by vitamin E deficiency, there can be an increase in reticulocytes, and the size of red blood cells can be seen in blood films. Heterogeneous, fragmented and spherical, polyphilic erythrocytes. Folic acid deficiency is seen as a tendency to hyperfoliation of neutrophils, with lobulation of 5 or more lobes or 4 or more lobes in >80% of cases. This suggests folic acid deficiency. 2, serum ferritin value can be decreased; 3, serum vitamin E value can be decreased; 4, serum or red blood cell folate value can be decreased; 5, plasma erythropoietin can be low. V. Prevention and control 1. Promote breastfeeding and reasonable addition of complementary foods. 2, iron: regardless of breastfeeding or fresh milk feeding, early iron supplementation is required. Premature infants generally start iron supplementation at 8 weeks after birth. The preventive amount of elemental iron is Q2mg/kg per day, divided into oral doses, the maximum amount of daily does not exceed 15mg for 12-15 months. Vitamin C can be taken orally at the same time to enhance the absorption of iron. Premature infant formula (fortified with iron) can also be consumed. 3. Vitamin E: Give 10-15mg daily until 8-10 weeks of age after birth, which can effectively prevent hemolytic anemia caused by vitamin E deficiency. The treatment amount is 50-200mg/day for 2 weeks, which can correct hemolytic anemia. 4. Folic acid: The daily requirement for premature babies is 50ug, and those with existing diseases should be supplemented with 100ug/day. Generally, the serum folic acid level has returned to normal in 6-8 months after birth. Therapeutic dose: 100-200ug/day, daily or intramuscular injection for 5-7 days. 5.Blood transfusion: Indications for blood transfusion: in neonatal period, Hb below 100g/L or below 110g/L with shortness of breath, asphyxia, slow heart rate, recurrent apnea, increased heart rate (excluding pneumonia, fever), slow weight gain. 2-4 months, below 90g/L, gestational age less than 30 weeks, hematocrit below before blood transfusion; but when combined with severe pneumonia, below also be transfused. 6, recombinant human erythropoietin: (1) dose; (2) duration of treatment; (3) course of treatment and route of administration; (4) iron supplementation: support erythropoiesis. Foreign reports 1-6mg/kg/d, oral or intravenous administration. The optimal dose and route of administration remain to be explored.