Contribution of iron status at birth to infant iron status at 9 months: data from a prospective maternal-infant birth cohort in China.

BACKGROUND/

OBJECTIVES

The contribution of iron status at birth to iron status in infancy is not known. We used a physiologic framework to evaluate how iron status at birth related to iron status at 9 months, taking iron needs and sources into account.

SUBJECTS/

METHODS

In a longitudinal birth cohort in China, iron status measures in cord blood and venous blood in infancy (9 months) and clinical data were prospectively collected in 545 healthy term maternal-infant dyads. We used structural equation modeling (SEM) to create a 9-month iron composite and to assess direct and indirect contributions of multiple influences on 9-month iron status. Logistic regression was used to calculate odds ratios for iron deficiency (ID), iron deficiency anemia (IDA), and anemia.

RESULTS

Approximately 15% (78/523) of infants were born with cord SF <75 µg/l, suggesting fetal-neonatal ID. At 9 months, 34.8% (186/535) and 19.6% (105/535) of infants had ID and IDA, respectively. The following factors were independently associated with poorer 9-month iron status: higher cord zinc protoporphyrin/heme (ZPP/H) (adjusted estimate -0.18, P < 0.001) and serum transferrin receptor (sTfR) (-0.11, P = 0.004), lower cord hemoglobin (Hb) (0.13, P = 0.004), lower birth weight (0.15, P < 0.001), male sex (0.10, P = 0.013), older age at testing (-0.26, P < 0.001), higher 9-month weight (-0.12, P = 0.006) and breastfeeding (0.38, P < 0.001). Breastfeeding at 9 months showed the strongest association, adjusting for all other factors. Compared to formula-fed infants, the odds of IDA were 19.1 (95% CI: 6.92, 52.49, P < 0.001) and 3.6 (95% CI: 1.04, 12.50, P = 0.043) times higher in breastfed and mixed-fed infants, respectively.

CONCLUSIONS

Indicators of iron status at birth, postnatal iron needs, and iron sources independently related to iron status at 9 months. Sex was an additional factor. Public health policies to identify and protect infants at increased risk of ID should be prioritized.