Effects of routine oral iron supplementation with or without folic acid for women during pregnancy

  • Review
  • Intervention


  • Juan Pablo Peña-Rosas,

    Corresponding author
    1. U.S. Centers for Disease Control and Prevention (CDC), International Micronutrient Malnutrition Prevention and Control Program (IMMPaCt), Atlanta, GA, USA
    • Juan Pablo Peña-Rosas, Reduction of Micronutrient Malnutrition Unit, Department of Nutrition for Health and Development, World Health Organization, 20 Avenue Appia, Geneva 27, 1211, Switzerland. penarosasj@who.int.

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  • Fernando E Viteri

    1. Children's Hospital and Oakland Research Institute, Oakland, CA, USA
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It has been suggested that routine intake of supplements containing iron or combination of iron and folic acid during pregnancy improves maternal health and pregnancy outcomes.


To assess the efficacy, effectiveness and safety of routine antenatal daily or intermittent iron supplementation with or without folic acid during pregnancy on the health of mothers and newborns.

Search strategy

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (June 2005). Additionally, we contacted relevant organizations for the identification of ongoing and unpublished studies.

Selection criteria

All randomised or quasi-randomised trials evaluating the effect of routine supplementation with iron or combination of iron and folic acid during pregnancy.

Data collection and analysis

We assessed trials for methodological quality using the standard Cochrane criteria. Two authors independently assessed the trials for inclusion and one author extracted data. We collected information on randomisation method, allocation concealment, blinding and loss to follow up. The primary outcomes included maternal and infant clinical and laboratory outcomes.

Main results

Forty trials, involving 12706 women, were included in the review. Overall, the results showed significant heterogeneity across most prespecified outcomes. Heterogeneity could not be explained by standard sensitivity analyses including quality assessment; therefore, all results were analysed assuming random-effects. Very limited information related to clinical maternal and infant outcomes was available in the included trials.

The data suggest that daily antenatal iron supplementation increases haemoglobin levels in maternal blood both antenatally and postnatally. It is difficult to quantify this increase due to significant heterogeneity between the studies. Women who receive daily antenatal iron supplementation are less likely to have iron deficiency and iron-deficiency anaemia at term as defined by current cut-off values. Side-effects and haemoconcentration are more common in women who receive daily iron supplementation. No differences were evident between daily and weekly supplementation with regards to gestational anaemia; haemoconcentration during pregnancy appears less frequent with the weekly regimen. The clinical significance of hemoconcentration defined as haemoglobin greater than 130 g/L remains uncertain.

Authors' conclusions

Further studies are needed to assess the effects of routine antenatal supplementation with iron or a combination of iron and folic acid on clinically important maternal and infant outcomes.

Plain language summary

Effects of routine oral iron supplementation with or without folic acid for women during pregnancy

There is not enough evidence to determine with confidence if routine daily or intermittent iron or iron-folic acid supplementation in pregnancy improves functional and health outcomes for women and babies.

During pregnancy, the mother and the baby need iron and folate to meet maternal needs and for the baby to develop properly. There is concern that the mother may become deficient in these nutrients and unable to sufficiently supply them to her baby. Low iron and folate levels can cause anaemia, which can make women tired, faint and be at increased risk of infection. These deficiencies could impact the mother and her pregnancy and the baby. The review of 40 trials, involving 12706 women, on routine antenatal iron or combination of iron with folic acid found insufficient data to evaluate these outcomes. Laboratory tests were reported but their functional significance is uncertain. More research is needed on preventive programs, particularly in income-poor countries.