Background Preterm and low birth weight infants are born with low stores in zinc, which is a vital trace element for growth, cell differentiation and immune function. Preterm infants are at risk of zinc deficiency during the postnatal period of rapid growth. Systematic reviews in the older paediatric population have previously shown that zinc supplementation potentially improves growth and positively influences the course of infectious diseases. In paediatric reviews, the effect of zinc supplementation was most pronounced in those with low nutritional status, which is why the intervention could also benefit preterm infants typically born with low zinc stores and decreased immunity.
Objectives To determine whether enteral zinc supplementation, compared with placebo or no supplementation, affects important outcomes in preterm infants, including death, neurodevelopment, common morbidities and growth.
Search methods Our searches are up‐to‐date to 20 February 2020. For the first search, we used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2017, Issue 8), MEDLINE via PubMed (1966 to 29 September 2017), Embase (1980 to 29 September 2017), and CINAHL (1982 to 29 September 2017). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials (RCTs) and quasi‐RCTs. We ran an updated search from 1 January 2017 to 20 February 2020 in the following databases: CENTRAL via CRS Web, MEDLINE via Ovid, and CINAHL via EBSCOhost.
Selection criteria We included RCTs and quasi‐RCTs that compared enteral zinc supplementation versus placebo or no supplementation in preterm infants (gestational age < 37 weeks), and low birth weight babies (birth weight < 2500 grams), at any time during their hospital admission after birth. We included zinc supplementation in any formulation, regimen, or dose administered via the enteral route. We excluded infants who underwent gastrointestinal (GI) surgery during their initial hospital stay, or had a GI malformation or another condition accompanied by abnormal losses of GI juices, which contain high levels of zinc (including, but not limited to, stomas, fistulas, and malabsorptive diarrhoea).
Data collection and analysis We used the standard methods of Cochrane Neonatal. Two review authors separately screened abstracts, evaluated trial quality and extracted data. We synthesised effect estimates using risk ratios (RR), risk differences (RD), and standardised mean differences (SMD). Our primary outcomes of interest were all‐cause mortality and neurodevelopmental disability. We used the GRADE approach to assess the certainty of evidence.
Main results We included five trials with a total of 482 preterm infants; there was one ongoing trial. The five included trials were generally small, but of good methodological quality. Enteral zinc supplementation compared to no zinc supplementationEnteral zinc supplementation started in hospitalised preterm infants may decrease all‐cause mortality (between start of intervention and end of follow‐up period) (RR 0.55, 95% CI 0.31 to 0.97; 3 studies, 345 infants; low‐certainty evidence). No data were available on long‐term neurodevelopmental outcomes at 18 to 24 months of (post‐term) age. Enteral zinc supplementation may have little or no effect on common morbidities such as bronchopulmonary dysplasia (RR 0.66, 95% CI 0.31 to 1.40, 1 study, 193 infants; low‐certainty evidence), retinopathy of prematurity (RR 0.14, 95% CI 0.01 to 2.70, 1 study, 193 infants; low‐certainty evidence), bacterial sepsis (RR 1.11, 95% CI 0.60 to 2.04, 2 studies, 293 infants; moderate‐certainty evidence), or necrotising enterocolitis (RR 0.08, 95% CI 0.00 to 1.33, 1 study, 193 infants; low‐certainty evidence).The intervention probably improves weight gain (SMD 0.46, 95% CI 0.28 to 0.64; 5 studies, 481 infants; moderate‐certainty evidence); and may slightly improve linear growth (SMD 0.75, 95% CI 0.36 to 1.14, 3 studies, 289 infants; low‐certainty evidence), but may have little or no effect on head growth (SMD 0.21, 95% CI ‐0.02 to 0.44, 3 studies, 289 infants; moderate‐certainty evidence).
Authors' conclusions Enteral supplementation of zinc in preterm infants compared to no supplementation or placebo may moderately decrease mortality and probably improve short‐term weight gain and linear growth, but may have little or no effect on common morbidities of prematurity. There are no data to assess the effect of zinc supplementation on long‐term neurodevelopment.
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