BACKGROUND:Iron deficiency anemia is the most common nutritional disorder in the world. It is a major public health problem particularly among pregnant women with adverse effects on the mother and the new born. Iron supplementation is universally recommended to correct or prevent iron deficiency. AIMS & OBJECTIVE: The present study was conducted to compare the efficacy and tolerability of three oral iron preparations in anemic pregnant women of more than 14 weeks of gestation. MATERIALS AND METHODS: Randomized Control trial, done at Tagore Medical College and Hospital, Chennai. 60 antenatal women were selected; they were divided into three groups, 20 in each group. They were treated with Carbonyl iron, ferrous sulphate and ferrous fumarate. Hemoglobin estimation was done at 0 day, 30 th and 60 th day. Adverse effects were monitored. RESULTS: Data analysis showed an increase in haemoglobin levels in all three groups after the 30 th day (p<0.05). Carbonyl iron showed highly significant increase (p<0.05) in the haemoglobin level as compared to the other two drugs at the end of the 60 th day. CONCLUSION: Carbonyl iron is superior in efficacy when compared to ferrous sulphate and ferrous fumarate and is better tolerated. So carbonyl iron is safe in pregnancy and can be given as a supplement to treat iron deficiency anemia during pregnancy. KEYWORDS: Antenatal women, carbonyl iron, iron deficiency anemia. INTRODUCTION:Anemia is a global public health problem. In pregnant women anemia is due to iron deficiency, which is the most common nutrient deficiency in the world. According to WHO data, prevalence of anemia in pregnant women is 14% in developed countries and 51% in developing countries. [1] In India the prevalence of anemia is 65-75% in pregnant women, this high prevalence is due to poor socioeconomic status, dietary habits, poor health status, multi parity and less birth spacing.20% of all maternal deaths are contributed to anemia. [2,3] Anemia is defined as a qualitative or quantitative deficiency of circulating haemoglobin, leading to decreased oxygen carrying capacity of the red blood cells to the tissues. [4] It is divided into three degrees, mild (10.9-9.0 gm %), moderate (8.9-7.0 gm %) and severe (<7.0 gm %). [5] During pregnancy, women go through a variety of physiological changes especially in the blood circulatory system. Average iron requirement is 4 mg/ day throughout pregnancy; this varies from 2.5 mg/day in early pregnancy to 6-8 mg/day from 32 weeks onwards. Iron deficiency anemia occurs because of the increased iron requirements that are needed to supply the expanding blood volume of the mother and the rapidly growing fetus and placenta.Iron absorption in food is less than 10%, this requires at least 40-60 mg of iron in the diet to achieve 4-6 mg of absorption and if the pre pregnancy iron stores are low then the amount of iron needed during the last half of the pregnancy cannot be met with diet alone. [6,7]