Are prenatal Fe supplements doing more harm than good?

Iron supplementation during mid-pregnancy is associated with a higher likelihood of gestational diabetes, hypertension, and metabolic syndrome, according to a study in the August issue of the American Journal of Obstetrics and Gynecology.

Simona Bo, MD, and colleagues from the University of Turin in Italy examined the association between iron supplementation and metabolic or hypertensive abnormalities during mid-pregnancy (24-28 weeks) in 1,000 women. Of these, 500 had gestational diabetes mellitus and 212 used iron supplements.

The researchers found that iron supplement users had a higher prevalence of gestational diabetes mellitus (70.8% vs. 44.4%), hypertension (25.9% vs. 9.8%), and metabolic syndrome (25.9% vs. 10.4%). After adjusting for multiple confounders, the risk was two- to threefold higher for each condition. Women in both groups who took iron supplements had significantly higher values on the glucose tolerance test.

“Iron supplementation is associated with glucose impairment and hypertension in mid-pregnancy; its potential harmful effects might be carefully debated regarding its effectiveness,” Bo and colleagues conclude.

Bo S, Menato G, Villois P, et al. Iron supplementation and gestational diabetes in midpregnancy. Am J Obstet Gynecol. 2009;201:158.e1-6.