Iron deficiency is the most common nutritional deficiency globally. Children and women of reproductive age are at a particular risk of iron deficiency. Anaemia during pregnancy is a specific risk factor for adverse maternal and perinatal outcomes. The objective of this review was to assess the impact of routine iron supplementation on maternal anaemia and perinatal outcomes. A literature search was conducted for published randomised and quasi-randomised trials on PubMed and the Cochrane Library. Only those studies were included in the review that assessed the preventive effect of iron supplementation during pregnancy. Data from selected studies were double abstracted in a standardised excel sheet. The studies were graded according to study design, limitations, intervention specifics and outcome effects. Meta-analyses were conducted where data were available from more than one study for an outcome. After screening 5209 titles, 30 studies were selected for inclusion in this review. Daily iron supplementation resulted in 69% reduction in incidence of anaemia at term in the intervention group compared with control [relative risk (RR) 0.31 [95% confidence interval (CI) 0.22, 0.44]] and 66% reduction in iron deficiency anaemia at term (RR 0.44 [95% CI 0.28, 0.68]; random model) compared with no intervention/placebo. The quality grade for these outcomes was that of ‘moderate’ level. Routine daily iron supplementation during pregnancy resulted in a significant reduction of 20% in incidence of low birthweight in the intervention group compared with control (RR 0.80 [95% CI 0.71, 0.90]). Preventive iron supplementation during pregnancy has a significant benefit in reducing incidence of anaemia in mothers and low birthweight in neonates.