OBJECTIVE: To define criteria based on iron status parameters for the identification of healthy women who do need/do not need iron supplementation during normal pregnancy. METHODS: Randomized, double-blind, placebo-controlled study of 113 women (62 iron-, 51 placebo treated) and their newborns. Iron dose was 66 mg elemental iron as ferrous fumarate daily from 14–18 weeks gestation to delivery. Hemoglobin (Hb), serum (S)-ferritin, S-transferrin saturation percentage, and S-erythropoietin were measured during gestation, prepartum, one week and 8 weeks postpartum. The women were divided in groups according to S-ferritin levels at inclusion:<30,≥30,≥40,≥50 and≥60μg/L. Iron deficiency (ID) was defined as S-ferritin < 15μg/L; iron deficiency anemia (IDA) as S-ferritin < 15μg/L and Hb < 110 g/L. RESULTS: Placebo treated women with S-ferritin levels < 30μg/L at inclusion had a much higher incidence of ID/IDA than placebo treated women with S-ferritin levels≥30,≥40,≥50, and≥60μg/L. S-ferritin levels≥40μg/L were associated with a very low risk of ID/IDA and none of the women with levels≥50 and≥60μg/L displayed ID/IDA. CONCLUSIONS: Women having S-ferritin < 30μg/L in early pregnancy, have a high risk of ID/IDA and should be recommended ferrous iron supplements in appropriate doses. With increasing iron reserves, i.e., increasing S-ferritin, the need for iron supplements diminishes, and placebo treated women having S-ferritin ≥40μg/L seldom develop IDA. Women with S-ferritin levels≥50 and≥60μg/L or higher, have adequate iron reserves and do not need routine iron prophylaxis in pregnancy. The results support the arguments for an individual iron supplementation guided by iron status, to avoid unwanted side effects of unnecessary iron intake.