BACKGROUND: Iron deficiency (ID) can occur among exclusively breastfed infants before 6 mo of age. OBJECTIVE: The objective was to determine which subgroups of fully breastfed infants are at highest risk of ID. DESIGN: We assessed the prevalence of ID (ferritin < 12 mug/L) and iron deficiency anemia (IDA; ferritin < 12 mug/L and hemoglobin < 105 g/L) and risk factors associated with ID and IDA at 6 mo among 404 fully breastfed infants with a birth weight >2500 g from 6 studies in Ghana, Honduras, Mexico, and Sweden. Infants with an elevated C-reactive protein concentration (8%) were excluded. RESULTS: The percentages of infants with ID were 6% in Sweden, 17% in Mexico, 13-25% in Honduras, and 12-37% in Ghana. The percentages with IDA were 2% in Sweden, 4% in Mexico, 5-11% in Honduras, and 8-16% in Ghana. With data pooled, the key predictors of ID (20%) were male sex [adjusted odds ratio (AOR): 4.6; 95% CI: 2.5, 8.5] and birth weight 2500-2999 g (AOR: 2.4; 95% CI: 1.4, 4.3). The predictors of IDA (8%) were male sex (AOR: 7.6; 95% CI: 2.5, 23.0), birth weight of 2500-2999 g (AOR: 3.4; 1.5, 7.5), and weight gain above the median since birth (AOR: 3.4; 95% CI: 1.3, 8.6). The combination of birth weight 2500-2999 g or male sex had a sensitivity of 91% for identifying ID and of 97% for identifying IDA. CONCLUSIONS: Among fully breastfed infants with a birth weight >2500 g, IDA is uncommon before 6 mo, but male infants and those with a birth weight of 2500-2999 g are at higher risk of ID and IDA.
2009. Vol. 89, no 5, 1433-1440 p.