Iron Supplementation in Pregnancy and Risk of Gestational Diabetes: A Narrative Review

Abstract

Pregnant women frequently supplement their diets with iron to treat any cryptic anemia, on the assumption that if anemia is not present, there will be no negative consequences. However, in women who are already iron-replete, it has been suggested that this can lead to iron overload and an increased risk of certain pregnancy complications. One such complication is gestational diabetes. Fourteen clinical trials, case–control or cohort studies (found using Pubmed/Scopus/Web of Science) have investigated links between iron supplementation in pregnancy and risk of gestational diabetes, several of them finding significant associations with increased risk. Potential mechanisms include increased oxidative stress leading to insulin resistance and inadequate compensatory insulin secretion. Current evidence suggests that dietary supplementation with iron in pregnancy may increase a pregnant woman’s chance of developing gestational diabetes, although available evidence is somewhat contradictory, and the magnitude of any increased risk appears relatively small. Meta-analyses have suggested the presence of significant heterogeneity in results between studies, urging a degree of caution in interpreting these results. It is currently suggested that advice to pregnant women about whether to supplement their diets with iron or not should consider both their current iron status and their other established risk factors for gestational diabetes.

Molecular pathways and nutrigenomic review of insulin resistance development in gestational diabetes mellitus

“…However, contradictory findings have been reported, with some researchers finding no adverse effects of iron supplementation on pregnant women ( 181 , 182 ). Nevertheless, it is crucial to monitor iron levels before considering it as a supplement due to its potential impact on glucose metabolism and insulin resistance ( 183 ).…”

Dietary supplements, guideline alignment and biochemical nutrient status in pregnancy: Findings from the Queensland Family Cohort pilot study

“…with an increased risk of developing gestational diabetes and increased offspring adiposity (Petry et al, 2020), which may be attributed to high doses of elemental iron (Petry, 2022), and MMN supplementation >5 times per week has been associated with an increased risk of autism spectrum disorder in offspring (Raghavan Note: Estimates (unstandardized coefficients) refer to how much the mean daily dose of supplemental nutrient varied by each maternal characteristic when all other characteristics were held constant.…”

“…It is therefore unknown whether MMN supplementation offers benefits that are superior to folic acid and iodine alone, and other micronutrients when indicated (e.g., iron), nor when taken beyond the first trimester. Although research is limited, MMN supplementation in high‐income countries has been associated with an increased risk of developing gestational diabetes and increased offspring adiposity (Petry et al, 2020 ), which may be attributed to high doses of elemental iron (Petry, 2022 ), and MMN supplementation >5 times per week has been associated with an increased risk of autism spectrum disorder in offspring (Raghavan et al, 2018 ). Despite this, there is the common belief that supplements are safe to take during pregnancy, even if one's diet is nutritionally adequate, and that excess nutrients are simply excreted by the body (Malek et al, 2018 ).…”

Using metabolomics and proteomics to identify the potential urine biomarkers for prediction and diagnosis of gestational diabetes

“… 99 Furthermore, some studies have found that iron overload is associated with an increased risk of GDM, with possible mechanisms including increased oxidative stress, which contribute to IR and inadequate insulin secretion. 100 In addition to collecting urine to assess changes in 8-OHdG, Tuna et al. collected blood to measure indicators related to blood glucose and iron status at 11∼14 weeks of gestation and 24∼28 weeks of gestation, including fasting blood glucose (FBG), HbA1c, ferritin and hemoglobin levels.…”