Hematological and iron content evolution in exclusively breastfed late-preterm newborns

OBJECTIVES: To analyze and compare the evolution of hematological parameters and body iron content between exclusively breastfed late-preterm and term newborns during the first two months of life. METHODS: Cohort study. Weight, length, head circumference, body mass index, hemoglobin, hematocrit, reticulocytes, total iron-binding capacity, transferrin saturation, serum iron and ferritin were measured in 25 late-preterm and 21 term newborns (at birth and at one and two months of age) who were exclusively breastfed. Statistical analysis: Kolmogorov-Smirnov test, one-way ANOVA or Kruskal-Wallis test; and Student's t-test or Mann-Whitney test. Significance: p<0.05. RESULTS: The corrected gestational ages of the late-preterm infants were 39.98 weeks at one month of life and 44.53 weeks at two months. Anthropometric measures and the body mass index increased over time (p<0.001) and hemoglobin, hematocrit, reticulocytes and body iron content decreased (p<0.001). Late-preterm infants at term corrected gestational age had reduced hemoglobin, hematocrit and reticulocyte concentrations, and reduced total iron-binding capacity (p<0.001) and serum iron (p = 0.0034) compared with values observed in term newborns at birth. Late-preterm newborns at a corrected gestational age of one month post-term had hemoglobin (p = 0.0002), hematocrit (p = 0.0008), iron (p<0.0001) and transferrin saturation (p<0.001) levels lower than those of term newborns at one month of age and a higher total iron-binding capacity (p = 0.0018). Ferritin did not differ between the groups. CONCLUSION: Exclusively breastfed late-preterm newborns presented greater reductions in hemoglobin/hematocrit and lower iron stores at a corrected gestational age of one month post-term than did term newborns, suggesting specific iron supplementation needs.