The purpose of this study is to determine whether iron-fortified PN is effective in the preventative and treatment of preterm infants. Preterm infants are at risk for anemia especially in preterm infants. Anemia effects growing development, clinical prognosis, cognition, movement, learning ability and behavioral development.

As enteral nutrition is not feasible soon after birth in most preterm infants, parenteral iron administration is an efficacious method for investigators to select. For most preterm infants, the use of parenteral nutrition(PN) is very common during the first ten days of life, so the investigators hypothesis that iron-fortified PN may have a preventative and treatment effect on preterm infants using PN as a supplementation of oral nutrition; Iron-fortified PN can also improve iron store status of preterm infants. The higher concentration of iron used in this study, the larger preventative or treatment effect on preterm infants anemia; it is safe to add small dose of iron agent to PN.

Infants are at risk for anemia especially in preterm infants. Generally the smaller birth weight and gestational age, the higher anemia ate in infants. As enteral nutrition is not feasible soon after birth in most preterm infants, parenteral iron administration is an efficacious method for investigators to select.

Meeting the Inclusion Criteria of this study will be randomly divided into five groups, control group, group1 (100μg/kg/d, and the highest concentration of iron is ≤0.8g/100ml PN), group2（200μg/kg/d, and the highest concentration of iron is ≤0.8g/100ml PN), group3 (300μg/kg/d, and the highest concentration of iron is ≤0.8g/100ml PN), group4 (400μg/kg/d, and the highest concentration of iron is ≤0.8g/100ml PN). Iron supplementation period for more than ten days. For five groups, complete blood counts, differential counts, and reticulocyte counts were measured weekly in samples obtained, serum iron, iron protein, total iron binding force were measured at baseline and after 2 weeks. Through comparative analysis of five groups, to find iron-fortified PN whether affect anemia rate and iron storage in premature infants. The investigators also selected malondialdehyde (MDA) and 8-isoprostaglandin F2α (8-iso-PGF2α) as the investigators concerns about iron used in PN induces oxidative stress index. Iron protein determination use radioimmunoassay method, serum iron and total iron binding force determination use chemical method, MDA and 8-iso-PGF2α determination use enzyme-linked immunosorbent assay method.

The investigators hypothesis that iron-fortified PN may have a preventative and treatment effect on preterm infants using PN as a supplementation of parenteral nutrition; Iron-fortified PN can also improve iron store status of preterm infants. The higher concentration of iron used in this study, the larger preventative or treatment effect on preterm infants anemia.

Inclusion Criteria:

• Preterm infants with birth weight less than 2kg
• Have parenteral nutrition indication
• With written informed consent of parents or guardian

Exclusion Criteria:

• Have already used PN before randomization
• Kidney and liver function abnormal
• Have hemolytic disease
• Have hemorrhagic disease
• Have Serious congenital malformation
• Have septicemia
• Have plethora newborn
• Use PN less than ten days