The authors report that 30 studies were included for review (number of participants unclear). The studies that investigated the impact of iron on low birthweight were judged high quality. The studies of anaemia at term, pre-term birth, small-for-gestational age and perinatal mortality were judged moderate outcome-specific quality. Perinatal mortality was judged as low out-come specific quality
Maternal outcomes: Iron or iron-folate supplementation during pregnancy significantly reduced incidence of maternal anaemia by 69% compared to placebo or no supplementation (RR 0.31, 95% CI 0.22 to 0.44; Ι²=72%; 18 studies; 8,665 participants). Subgroup analyses of iron only (RR 0.27, 95% CI 0.17 to 0.42) and iron plus folate (RR 0.38, 95% CI 0.18 to 0.80) also found significant benefits on maternal anaemia.
Frequency of dosage (intermittent supplementation versus daily supplementation) was not associated with any difference in the incidence of maternal anaemia. Iron/iron-folate supplementation significantly reduced the risk of iron deficiency anaemic at term (RR 0.44, 95% CI 0.28 to 0.68; Ι²=85%; seven studies) and need for transfusion (RR 0.61, 95% CI 0.38 to 0.96; Ι²=0%; three studies) compared to placebo or no supplementation. Iron supplementation did not significantly impact on severe anaemia at term or in the last two trimesters, post-partum haemorrhage or pre-eclampsia.
Infant outcomes: Iron or iron-folate supplementation during pregnancy was associated with significantly lower incidence of low birthweight than placebo or no supplementation (RR 0.80, 95% CI 0.71 to 0.90; Ι²=25%; 11 studies; 9,397 participants). Iron or iron-folate supplementation was associated with significantly greater mean birthweight (WMD 42.18, 95% CI 9.27 to 75.09; Ι²=54%; 13 studies) compared to placebo or no supplementation. There was no effect of iron supplementation on pre-term birth, perinatal mortality or small-for-gestational age.