Iron-deficiency anemia is still prevalent among pregnant women living in industrialized countries such as Canada. To prevent this deficiency, iron supplements (30 mg/d) are routinely prescribed to Canadian pregnant women. Recently, dietary reference intakes for iron have increased from 18 and 23 mg/d during the second and third trimesters, respectively, to 27 mg/d throughout the pregnancy for all age groups. Whether this new recommendation implies an increase of iron dosage in supplements has not been answered. Are there any benefits or risks for the mother and her infant associated with iron supplementation during pregnancy? If iron supplementation is recommended, what should be the ideal dosage? This article reviews current knowledge on the potential negative or positive impact of iron supplementation during pregnancy on the outcomes of both infants and mothers. Based on the literature reviewed, a low daily dose of iron (30 mg elemental iron) during pregnancy improves women's iron status and seems to protect their infants from iron-deficiency anemia. Several studies have also shown that a low daily dose of iron may improve birth weight even in non-anemic pregnant women. However, higher dosages are not recommended because of the potential negative effects on mineral absorption, oxidative pathways, and adverse gastrointestinal symptoms. To date, it is still not clear if health professionals should recommend routine or selective supplementation. However, neither routine nor selective iron supplementation during pregnancy is able to eliminate iron-deficiency anemia. Even though the dietary reference intake for iron during pregnancy has been recently increased, we do not recommend higher doses of iron in supplements designed for pregnant women.