Zinc supplementation and growth of infants born small for gestational age

To analyze the effect of zinc supplementation on postnatal growth of infants born small for gestational age, we selected 68 infants at birth and followed them monthly for 6 months. They were randomly assigned to a supplemented group (group S, n = 35) receiving 3 mg of Zn (acetate) per day, or to a placebo (group P, n = 33), in a double-blind study. Weight increments in group S were significantly higher than those in group P at 2 months (p < 0.003); z scores showed catch-up growth only in group S. Length increments were also greater in group S than in group P, ending at 6 months were 64.9 +/- 1.8 versus 63.4 +/- 3.5 cm (mean +/- SD; p < 0.01); changes in z scores for 6 months were -1.28 to -0.66 in group S and -1.43 to -1.47 in group P (p < 0.001). Weight-for-length improved similarly in both groups (z score, -2.2 to +0.2). The increase in weight-for-age was higher in group S girls (p < 0.034), ending at 6 months with -0.13 +/- 0.59, versus -0.52 +/- 0.62 in group S boys, -1.15 +/- 0.49 in group P girls, and -1.05 +/- 0.80 in group P boys (+/- SD). More infants in group P received cow milk-based formula before 4 months because of inadequate weight increments. An additive effect on weight increase was observed between Zn supplementation (p < 0.02), exclusive breast-feeding after 4 months of age (p < 0.001), and gender (p < 0.02). Plasma and hair Zn values showed a downward trend, less marked in group S than in group P. We conclude that Chilean infants born small for gestational age have better weight and linear growth during the first 6 months of life if they receive Zn supplementation.