Resident Physician University of Texas Southwestern Medical School Dallas, Texas, United States
Background: Zn deficiency is associated with prematurity, intrauterine growth restriction, and growth failure. Since most of Zn accretion in the fetus occurs in the 2nd and 3rd trimesters, preterm infants are at risk for Zn deficiency. Zn supplementation likely improves weight gain and linear growth. Among infants < 33 weeks GA or VLBW fed their own mother's milk and/or donor breast milk, 14% were diagnosed with Zn deficiency (serum Zn level < 0.74 mcg/ml) (Sanchez-Rosado 2023). Objective: To examine if routine enteral Zn supplementation to meet recommended requirements would positively impact growth parameters, such as weight, length, and fronto-occipital circumference (FOC), in infants born < 33 weeks GA or VLBW. Design/Methods: In Epoch-1, Zn supplementation in total parenteral nutrition (TPN) was 450 mcg/kg/day and enteral supplementation was provided only to those with documented Zn deficiency. In Epoch-2, Zn was provided with 500 mcg/kg/day in TPN (ESPGHAN) and routine enteral supplementation, to achieve a total of 2.5 and later 2.7-3 mg/kg/day (Koletzko 2021) until 36 weeks postmenstrual age (PMA) or discharge. In Epoch-2, serial Zn levels were obtained at birth, when the infant was at 140 ml/kg/day of feeds, and one month later. Growth was assessed by change in Z-scores from birth to discharge in accurate measurements of length (Δlengthz), weight, and FOC, adjusted for GA, sex, and PMA. Physiologic growth pattern was defined as < 1 Z-score decrease in growth parameters after 4 weeks of life. Results: Among 840 infants, birth characteristics were similar in both epochs (Table 1). Adjusted Δlengthz improved by 10% in Epoch-2 vs Epoch-1 (Table 2). However, there was no significant change in z-scores of weights and FOC. In Epoch-2 vs Epoch-1 more infants had physiologic growth patterns (56% vs 39%) (Table 1). In Epoch-2, 96% of the infants had Zn levels obtained; 15/244 (8.7)% were Zn-deficient within 48 hours postnatally and 144/280 (60%) had at least one low serum Zn level. Among 22-28 weeks GA infants, the frequency of low trough Zn level was higher in those with than in those without poor growth (82/93 (88%) vs 41/61 (67%), P=0.002).
Conclusion(s): In this study, routine enteral Zn supplementation in preterm or VLBW infants improved linear growth by 10% and overall growth pattern. Low serum Zn levels suggesting Zn deficiency occurred frequently despite Zn intake as currently recommended. However, persistent low Zn levels among infants with normal growth patterns might represent utilization/intracellular distribution of Zn rather than true deficiency. D368DFA2-BB52-4AF5-B3D8-9BFFE786AE3D_4_5005_c.jpeg
.jpg "Tina A. Seidu, MD, MHS (she/her/hers) photo")