Bethesda, MD—Should iron supplementation be recommended for pregnant women in light of new research showing a link between higher iron levels and gestational diabetes?

That was the question raised by research published recently in the journal Diabetologia.

The study team, led by researchers from the National Institutes of Health (NIH) and colleagues, reports on evidence that high levels of iron biomarkers in the body are associated with an increased risk of gestational diabetes (GDM) in pregnant women.

Background information in the article notes that pregnant women are especially vulnerable to iron deficiencies and related adverse pregnancy outcomes. The American Congress of Obstetricians and Gynecologists recommends screening and treatment only as necessary for iron deficiency, but some other groups, such as the World Health Organization (WHO) and the CDC, recommend routine iron supplementation for pregnant women, according to the study.

Noting emerging evidence of the possible link between higher iron stores and abnormal blood sugar control, including type 2 diabetes, in nonpregnant adults, researchers performed a case-control study of 107 GDM cases and 214 controls within the prospective, multiracial NICHD Fetal Growth Studies-Singleton Cohort (2009-2013). Several biomarkers of iron status, including plasma hepcidin, ferritin, and soluble transferrin receptor (sTfR) were monitored, and that information was used to calculate the sTfR:ferritin ratio, which captures both cellular iron need and availability of body iron stores.

The markers were measured twice before GDM diagnosis—gestational weeks 10-14 and 15-26—and twice afterwards—gestational weeks 23-31 and 33-39—with oral glucose-tolerance test results used to make the diagnoses.

Results indicate that, for both hepcidin and ferritin, in the second trimester of pregnancy, those in the top 25% of levels of these markers had about a 2.5 times increased subsequent risk of developing GDM, compared with those in the bottom 25%. Similar findings for ferritin levels were identified in the first trimester.

Study authors point out that, as a strong pro-oxidant, free iron can promote several cellular reactions that generate reactive oxygen species and increase the level of oxidative stress. Oxidative stress induced from excess iron accumulation can then cause damage to and death of pancreatic beta cells that produce insulin, they add, which, in turn, could contribute to impaired insulin synthesis and secretion.

In the liver, meanwhile, high iron stores might induce insulin resistance via impaired insulin signaling, as well as by limiting the capacity of the liver to extract insulin, the researchers explain.

“In summary, findings from this longitudinal and prospective study among multiracial, relatively healthy pregnant women without major pre-pregnancy chronic diseases, suggest that higher maternal iron stores may play a role in the development of GDM starting as early as the first trimester,” study authors conclude. “These findings are of clinical and public health importance as they extend the observation of an association between high body iron stores and elevated risk of glucose intolerance among non-pregnant individuals to pregnancy, and raise potential concerns about the recommendation of routine iron supplementation among pregnant women who already have sufficient iron.”

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