[Variations in serum ferritin and erythrocyte index in the first eight weeks of life in term newborn infants].

Objective: To describe changes in erythrocyte index during the first 8 weeks of life in neonates in relation to their iron store.

Material And Methods: We performed a longitudinal study of a group of healthy term newborn infants, in whom we evaluated erythrocyte index and serum ferritin (SF) values at birth and at weeks 4 and 8 of age. Depending on the comparison made in SF values between birth and 2 months, the infants were divided into two groups: group I (without variation in SF) and group II (with a decrease in SF).

Results: A total of 110 neonates were included, with 46 neonates in group I and 64 in group II. No differences in demographic or hematologic data were found, including neonates with anemia or a decrease in hemoglobin values (5.2 vs. 5.5 g/dL). SF decreased to lower values in group II than in group I (215 vs. 194 microg/L, p < 0.001), with a greater number of neonates with low iron stores at 2 months of age (0.15 vs. 0.37, p < 0.01; RR 2.464, 95 % CI: 1.162-5.227).

Conclusions: In healthy term newborn infants, erythrocyte index at birth showed no relation with iron store. SF values at 2 months of age depended on SF concentrations at birth. Decreased hemoglobin and SF values are part of physiological adaptation in the first few months of life.