The review included 25 studies (n =4,640). All were RCTs.
The funnel plot, Egger’s test and Begg’s rank correlation test did not indicate publication bias.
The studies assessing weight-for-age, weight-for-height and height-for-age were statistically heterogeneous (p<0.001).
The difference in change in weight-for-age between supplemented and control groups was statistically significant when p=0.5 (SMD 0.13, 95% confidence interval, CI: 0.01, 0.25, p=0.04). However, this result was not statistically significant when the SDs were calculated with the independence assumption p=0, with the post-test scores, or with the analytical components where the actual SDs were available (SMD 0.13, 95% CI: -0.05, 0.32, p=0.145).
Sensitivity analyses indicated that the change in weight-for-age was greater in studies carried out in malarial hyperendemic regions. It was also found that the effect size was greater in children aged over 5 years old for change in weight-for-height. Iron supplementation was also found to negatively affect the linear growth of children in developed countries (SMD -0.27, 95% CI: -0.49, -0.05, p=0.018), while supplementation for more than 6 months was associated with statistically significantly slower linear growth (SMD -0.13, 95% CI: -0.24, -0.01, p=0.039).
There was no statistically significant difference in overall weight-for-height, height-for-age, head circumference, subscapular skinfold thickness, triceps skinfold thickness or mid upper arm circumference between iron supplemented groups and control groups.
Further analyses for each of these outcomes were reported in the paper.