Exchangeable zinc pool size at birth is smaller in small-for-gestational-age than in appropriate-for-gestational-age preterm infants
2006
Krebs, Nancy F. | Westcott, Jamie L. | Rodden, Donna J. | Ferguson, Katharine W. | Miller, Leland V. | Hambidge, K Michael
BACKGROUND: Small-for-gestational-age (SGA) infants are susceptible to postnatal zinc deficiency, but whether this susceptibility is due to intrauterine factors or to high postnatal growth requirements is unknown. OBJECTIVE: We hypothesized that the size of the exchangeable zinc pool (EZP), which reflects metabolically available zinc, would be smaller in SGA than in appropriate-for-gestational-age (AGA) infants born prematurely. DESIGN: Intravenous ⁷⁰Zn (45 μg/kg) was administered to 10 SGA infants (8 boys) with a mean (±SD) gestational age of 33.3 ± 1.8 wk and to 11 AGA infants (8 boys) with a mean (±SD) gestational age of 32.4 ± 1.2 wk within 24 h of birth. The EZP was determined from isotope enrichment in spot urine collections on days 3-7. RESULTS: The mean birth weight of the SGA infants was 1.30 ± 0.2 kg and of the AGA infants was 1.84 ± 0.3 kg (P = 0.0001). The EZP size was significantly smaller in the SGA than in the AGA infants on an absolute basis (13.3 ± 2.8 and 25.2 ± 8.1 mg; P = 0.0002) and relative to body weight (10.3 ± 2.5 and 13.9 ± 4.5 mg/kg; P = 0.02). The difference remained significant after adjustment for gestational age and birth weight. CONCLUSION: These data provide evidence for differential zinc status at birth between SGA and AGA infants born prematurely at similar stages of gestation and offer at least a partial explanation for the reported benefits of postnatal zinc supplementation.
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