OBJECTIVE: To assess and compare the efficacy and safety of two and three doses of intravenous iron sucrose with daily oral ferrous sulphate in the prophylaxis of iron deficiency anaemia in pregnant women. STUDY DESIGN: 260 women with singleton pregnancy who met inclusion criteria and who gave informed consent were randomised between the 21st and 24th week into either the intravenous iron group or the oral iron group. Of 130 women in the intravenous iron group, 75 women received two doses of 200mg iron sucrose and 55 three doses of 200mg iron sucrose. The first dose was administered between the 21st and 24th gestational weeks, the second between the 28th and 32nd and the third between the 35th and 37th. The women of the oral group were given oral tablets of 80 mg ferrous sulphate daily, beginning on the day of study enrolment and stopping on the day of delivery. RESULTS: There was a non-significant trend to a higher frequency of responders (haemoglobin> or =11 g/dl) in the intravenous iron group (75 vs. 80%). There was a significant difference of repleted iron stores before delivery (ferritin>50 microg/l) in the group with three intravenous iron doses in comparison to the oral iron group (49 vs. 14%; p<0.001). No differences were observed in regard to maternal and perinatal outcomes. CONCLUSIONS: There was no clinically significant difference in the haematological, maternal and foetal outcomes in the parenteral route of iron prophylaxis in pregnant women.