Determinants of Plasma Zinc at 3 Months of Age in Rural Bangladeshi Infants From a Trial of Antenatal Multiple Micronutrient Supplementation

Objectives: Zinc is an essential trace element that serves as a cofactor for many metalloenzymes. Zinc deficiency is prevalent in South Asia, contributing to adverse maternal, birth, and offspring outcomes. We measured plasma zinc of 3-month-old infants in rural Bangladesh at the conclusion of a trial of a zinc-containing antenatal multiple micronutrient supplement (MMS) versus iron-folic acid (IFA) supplement to identify characteristics associated with infant zinc status. Methods: Within a cluster-randomized trial of antenatal (early pregnancy through 3 months postpartum) MMS, including 12 mg zinc, versus IFA, associations of infant zinc with maternal characteristics were examined in n=317 3-month-olds, a subset from mother-infant pairs in whom maternal zinc was measured in pregnancy and postpartum. The MMS versus IFA effect on zinc was tested by t-test, and multivariable generalized linear regression was used to examine associations with maternal factors, accounting for cluster. Results: There was no effect of MMS on infant zinc (p=0.56), which averaged 15.34 ± 0.36 μmol/L with 10.4% < 9.95 μmol/L, a cutoff for deficiency. Corresponding maternal plasma zinc in early pregnancy (pre-supplementation) was 11.00 ± 0.14 μmol/L, with 30.3% deficient. In adjusted analysis, infant zinc was associated with maternal early pregnancy but not late pregnancy, postpartum, or milk zinc, increasing 0.26 [95% CI: 0.03, 0.48] μmol/L per 1 μmol/L increment in maternal early pregnancy zinc (p=0.03). Infant zinc was 4.40 [0.15, 8.65] μmol/L higher among mothers >30 compared to < 20 years (p=0.04); conversely, parity of 1-3 was associated with 2.87 [-5.60, -0.13] μmol/L lower infant zinc compared to parity 0 (p=0.04). Conclusions: Infant zinc was also associated with non-modifiable maternal factors—that is, positively with age but inversely with parity. Infant zinc deficiency was present, although less common than among mothers, and findings suggest challenges in improving infant zinc status through maternal interventions during and after pregnancy. Further exploration of factors associated with infant zinc status is warranted. Funding Sources: Bill and Melinda Gates Foundation.