Background: The purpose of the present study was to evaluate the efficacy of low dose iron supplementation with and without a heme component, prescribed for women in the second half of pregnancy.

Method: A randomized, double-blind, placebo controlled trial. Thirty-one women received a daily dose of 27 mg elemental iron in a product containing both heme iron and non-heme iron (Hemofer), 30 women received the same dose as pure non-heme iron with vitamin C (Collets jern med vitamin C), and 29 women received placebo. A double dummy technique was used to mask tablets. The women were tested for red cell indices and iron status markers (s-ferritin, s-iron, Total Iron Binding Capacity and erythrocyte protoporphyrin) throughout pregnancy and 8 and 24 weeks postpartum. The results were analyzed according to the 'intention to treat' principle.

Results: The hematological effects were equal in the two treatment groups. 25% of the supplemented women fell below 110 g/l in Hb vs 52% in the placebo group (p < 0.05); none fell below 100 g/l in the supplemented groups, 14% in the placebo group. Iron status was significantly better for all measured parameters in the heme iron group compared to placebo at the end of pregnancy. Differences between the other groups were only shown for some parameters, probably due to the small sample size. In the heme iron group there were fewer women with empty iron stores postpartum than at the start of pregnancy (from 14% to 8%), in the non-heme iron group there was a significant increase (from 3% to 27%), and in the placebo group the percentage of women with empty iron stores was more than doubled (from 21% to 52%).

Conclusions: A daily dose of 27 mg elemental iron, containing a heme component, given in the second half of pregnancy, prevents depletion of iron stores after birth in most women. An equivalent dose of pure inorganic iron seems less effective, but the sample size in this study was too small to demonstrate significant differences between the two treatment groups.