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Iron prophylaxis during pregnancy - how much iron is needed? A randomized dose-response study of 20-80 mg ferrous iron daily in pregnant women



Iron prophylaxis during pregnancy - how much iron is needed? A randomized dose-response study of 20-80 mg ferrous iron daily in pregnant women



Acta Obstetrica et Gynaecologica Scandinavica 84(3): 238-247



Objective: To determine the lowest dose of iron for preventing iron deficiency and iron deficiency anaemia during pregnancy. Methods: In this randomized, double-blind, intention-to-treat study conducted between January 1995 and January 1997, a total of 427 healthy pregnant women from Denmark were allocated into four groups to receive ferrous iron (as fumarate) in doses of 20 mg (n=105), 40 mg (n=108), 60 mg (n=106), and 80 mg (n=108) from 18 weeks of gestation. Iron status markers (haemoglobin (Hb), serum ferritin, and serum soluble transferrin receptor (sTfR)) were measured at 18 weeks (inclusion), 32 weeks, and 39 weeks of gestation and 8 weeks postpartum. Side effects of iron supplements were recorded. Iron deficiency was defined as serum ferritin <13 micro g/litre and iron deficiency anaemia as serum ferritin <13 micro g/litre and Hb<5th percentile in iron replete pregnant women. Results: There were no significant differences between variables in the four groups at inclusion. At 32 and 39 weeks of gestation, the 20-mg fumarate group had significantly lower median serum ferritin (13 and 16 micro g/litre) than the 40-mg fumarate (17 and 21 micro g/litre), 60-mg fumarate (18 and 23 micro g/litre), and 80-mg fumarate groups (21 and 24 micro g/litre) (p<0.0001). At 32 and 39 weeks of gestation, women taking 20 mg fumarate had a significantly higher prevalence of iron deficiency (50 and 29%) than those taking 40 mg (26 and 11%), 60 mg (17 and 10%), and 80 mg (13 and 9%) of fumarate (p<0.001). The prevalence of iron deficiency anaemia at 39 weeks of gestation was significantly higher in women taking 20 mg (10%) than in those taking 40 mg (4.5%), 60 mg (0%), and 80 mg (1.5%) of fumarate (p=0.02). At 32 weeks of gestation, mean Hb in the 20-mg fumarate group was lower than the 80-mg fumarate group (p=0.06). There were no significant differences in iron status (ferritin, sTfR, and Hb) between subjects taking 40, 60, and 80 mg of fumarate. Postpartum, women taking 20 mg fumarate had significantly lower median serum ferritin than those taking 40, 60, and 80 mg fumarate (p<0.01). The prevalence of postpartum iron deficiency anaemia was low and similar in the four groups. The frequency of gastrointestinal symptoms was not significantly different in the four iron supplement groups and thus not related to the iron dose. Conclusion: In Danish women, a supplement of 40 mg ferrous iron/day from 18 weeks of gestation appears adequate to prevent iron deficiency in 90% of the women, and iron deficiency anaemia in at least 95% of the women during pregnancy and postpartum.

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Accession: 004213984

Download citation: RISBibTeXText

PMID: 15715531

DOI: 10.1111/j.0001-6349.2005.00610.x


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