This review was conducted to derive an umbrella summary of meta-analyses performed to evaluate the effects and associations of iron supplementation or iron status on maternal and birth/neonatal outcomes. Evidence from 16 meta-analyses suggests beneficial effects of multiple-micronutrient supplementation on some neonatal outcomes. Furthermore, higher ferritin levels seem to increase the risk for gestational diabetes mellitus, whereas maternal anemia was associated with adverse birth/neonatal outcomes.