Iron supplementation and gestational diabetes in midpregnancy

Association of mid-pregnancy ferritin levels with postpartum glucose metabolism in women with gestational diabetes

BACKGROUND

Ferritin, a key indicator of body iron levels, has been reported to associate with type 2 diabetes (T2DM) and the onset of Gestational diabetes mellitus (GDM). However, limited research explores the association between mid-pregnancy ferritin levels and the risk of postpartum abnormal glucose metabolism (AGM) in patients with GDM.

METHODS

A retrospective cohort study was conducted in 1514 women with GDM recruited from January 2016 to January 2021, and 916 women were included. Demographic characteristics, medical history and family history, pregnancy complications were recorded. Multiple logistic regression models were performed to assess the association between mid-pregnancy ferritin levels and the risk of postpartum AGM.

RESULTS

Following the postpartum oral glucose tolerance test, 307 (33.5%) exhibited AGM. The AGM group had higher mid-pregnancy serum ferritin levels [AGM vs NGT: 23 (11.7, 69) µg/L vs 17.80 (9.85, 40.7) µg/L, P < 0.001] and had a larger proportion of women with ferritin levels ≥30 µg/L (AGM vs NGT: 43.6% vs 31.4%, P < 0.001). Logistic regression analysis demonstrated that women with ferritin levels≥ 30 µg/L had a 1.566 times higher risk of developing postpartum AGM.

CONCLUSIONS

These findings indicate that elevated mid-pregnancy ferritin levels are significantly and independently associated with increased postpartum AGM risk in women with previous GDM. Consequently, cautious consideration is necessary for prescribing iron supplements in prenatal care, particularly for non-anemic women with GDM at high risk of developing diabetes after delivery.

The protective association of dairy intake and the adverse impact of iron on gestational diabetes risk

Background: Gestational diabetes (GDM) is a pregnancy-related glucose intolerance with significant implications for maternal and fetal health. Calcium is essential for insulin secretion and metabolism, while iron intake may also impact GDM. This case-control study was conducted to investigate the relationship between calcium and iron intake with the risk of GDM. Methods: GDM was defined as Fasting Blood Sugar>92mg/dL or 75g Oral-Glucose-Tolerance-Test 120-minutes>153mg/dL. A 168-Item food-frequency-questionnaire was used to collect dietary calcium and iron intake from 24-40 weeks of gestation. The impact of total iron, red, processed/unprocessed meat consumption, calcium, and dairy intake on GDM were investigated. Results: A total of 229 GDM and 205 non-GDM women (18-45 years) participated. GDM group had higher pre-pregnancy weight, weight gain, and pre-pregnancy BMI. Across all models, GDM risk significantly increased in the third and fourth quartiles of iron intake. The fourth quartile had an Odds Ratio (OR) of 2.68 (CI 95%, 4.89-1.56; P<0.001) compared to the reference. Heme-iron consumption in the fourth quartiles increased GDM risk. In the second calcium intake model, ORs for the second, third, and fourth quartiles were 0.51 (CI 95%, 0.91-0.25), 0.43 (CI 95%, 0.77-0.24), and 0.35 (CI 95%, 0.63-0.19), respectively (P<0.001 all), reducing GDM risk by 50-65% compared to the first quartile. Dairy consumption in all quartiles of the first and second models was associated with lower GDM risk. Conclusions: Consumption of heme-iron through red and processed meat associated with an increased chance of developing GDM. Dairy intake reduces the chances of developing GDM in pregnant women.

Ferritin and iron supplements in gestational diabetes mellitus: less or more?

Iron metabolism has been found to be closely related to gestational diabetes mellitus (GDM). Excessive ferritin levels were shown to be related to an increased risk of GDM because of iron overload which may lead to insulin resistance and β-cell injury by enhancing oxidative stress and inflammatory responses. On the contrary, insufficient ferritin levels can cause a number of obstetric complications, such as high incidence rates of anaemia and gestational hypertension. Therefore, high or low ferritin levels may have adverse effects on the mother and the foetus, putting clinicians in a dilemma when giving pregnant women iron supplements. This also explains why there have been more conflicting findings in the studies on dietary or oral iron supplementation during pregnancy. Hence, there is an urgent need for more evidence and strategies for appropriate recommendations for ferritin levels and iron supplementation during pregnancy to prevent iron insufficiency without causing iron overload and increasing the risk of GDM. Therefore, we gave an updated review on the association of GDM with ferritin metabolism, ferritin levels and iron supplementation based on the summary of the latest research.

Association of MTHFD1 G1958A Polymorphism with Gestational Diabetes Mellitus

Background The MTHFD1 G1958A polymorphism is a common variation in the gene encoding methylenetetrahydrofolate dehydrogenase 1 (MTHFD1), an enzyme crucial for folate metabolism. This study investigated the association between the MTHFD1 G1958A polymorphism, which is involved in folate metabolism, and gestational diabetes mellitus (GDM) risk. Methods A case-control study was conducted and 304 pregnant women (152 with gestational diabetes as cases and 152 healthy pregnant as controls) participated in the study. The polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) techniques were used to determine the MTHFD1 1958G>A polymorphism genotypes. Results Analysis of genotype frequencies revealed a statistically significant difference (p-value < 0.05) between the GDM group and the control group, suggesting a potential association between this gene variant and the development of GDM. Interestingly, while allele frequencies alone did not show a significant association with GDM risk, analysis in a recessive model (both severe and mild forms) demonstrated a strong link between the homozygous AA genotype and increased susceptibility to GDM. Conclusion This study provides the first evidence linking the MTHFD1 G1958A polymorphism and GDM risk in an Indian setting. These findings warrant further investigation into the functional impact of the MTHFD1 G1958A polymorphism and its potential role in the pathogenesis of GDM.

Association between iron-folic acid supplementation and pregnancy-induced hypertension among pregnant women in public hospitals, Wolaita Sodo, Ethiopia 2021: a case- control study

BACKGROUND

Pregnancy-induced hypertension is the new onset of high blood pressure after 20 weeks of gestation in women with previously normal blood pressure. To the best of our knowledge, no study has been conducted in our country to investigate the association between this pregnancy problem and iron-folic acid supplementation. The aim of this study was to determine the association between iron-folic acid supplementation and pregnancy-induced hypertension (PIH) in pregnant women at public hospitals in the Wolaita Sodo zone.

METHODS

An institution-based case-control study was conducted among pregnant women who visited public hospitals in the Wolaita Sodo zone from March 3, 2022, to August 30, 2022. A consecutive sampling method was used to select the study participants. The total sample size was 492, of which 164 were cases and 328 were controls. The data were collected by conducting face-to-face interviews and measurements. The data were entered into EpiData version 4.6 and exported to STATA 14 for analysis. Those variables with a p-value less than 0.05 were considered statistically significant. Descriptive statistics and odds ratios were presented using texts, tables, and figures.

RESULTS

A total of 471 women participated in this study, yielding a response rate of 96%. The cases had a mean age of 25 ± 4.43, while the controls had a mean age of 25 ± 3.99. The mean age at first pregnancy among cases was 20 ± 2.82 and among controls was 20 ± 2.97. The average number of deliveries for cases and controls was 1.97 ± 1.41 and 1.95 ± 1.38, respectively. There is no significant association between iron-folic acid supplementation and PIH. Pregnant women with high hemoglobin levels had higher odds of PIH as compared to those without it (AOR = 3.65; 95% CI: 1.0-12.9). Eating kocho (AOR = 14.4; 95% CI: 1.2-16.7) was positively associated with PIH.

CONCLUSIONS

There is no association between iron-folic acid supplementation during pregnancy and pregnancy-induced hypertension. Pregnant women with high hemoglobin levels had higher odds of PIH as compared to those without it. There is an association between kocho consumption and PIH. More research should be done using stronger designs.

Impact of iron supplementation on gestational diabetes mellitus: A literature review

Gestational diabetes mellitus (GDM) is a common complication of pregnancy, affecting 14% of pregnancies worldwide, and the prevention of pathological hyperglycaemia during pregnancy is meaningful for global public health. The role of iron supplementation in the progression of GDM has been of significant interest in recent years. Iron is a micronutrient that is vital during pregnancy; however, given the toxic properties of excess iron, it is probable that prophylactic iron supplementation will increase the risk of adverse pregnancy outcomes, including GDM. It is critical to clarify the effect of iron supplementation on the risk of GDM. Therefore, in this review, we comprehensively assess the role of iron in pregnancy. This review aimed to analyse the necessity of iron supplementation and maintenance of iron homeostasis during pregnancy, particularly reviewing the role and function of iron in beta cells and examining the mechanisms of excess iron contributing to the pathogenesis of GDM. Moreover, we aimed to discuss the association of haemoglobin and ferritin with GDM and identify priority areas for research.

The association of iron status, supplement iron in the first-trimester pregnancy with gestational diabetes mellitus: A nested case-control study

AIMS

The objective of this study was to examine whether the level of iron and iron supplements in the first-trimester pregnancy is associated with gestational diabetes mellitus (GDM).

METHODS

This was a nested case-control study using data from an established cohort in the Hunan Provincial Maternal and Child Health Hospital (HPMCHH) in South China. A total of 119 patients with GDM and 238 controls were enrolled in the study. Iron status indicators were tested in early pregnancy. Information on iron supplements use was collected by questionnaires. Binary logistic regression was used to obtain odds ratio (OR). The relative excess risk of interaction (RERI) was applied to evaluate the interaction.

RESULTS

We observed that pregnant women with normal ferritin levels (≥30 ng/ml) and iron supplements were associated with a 3.701-fold increased risk of GDM (OR: 3.701, 95% CI: 1.689-8.112) compared with the ferritin <30 ng/ml and without iron supplements group. Similarly, pregnant women with normal serum iron (SI) levels (≥9 μmol/L) and iron supplements were associated with a 5.447-fold increased risk of GDM (OR: 5.447, 95% CI: 2.246-13.209) compared with the SI < 9 μmol/L and without iron supplement group. We found an additive interaction between ferritin and iron supplements on the presence of GDM (RERI: 1.164, 95%CI: 0.333-1.994) and SI and iron supplements on the risk of GDM (RERI: 6.375, 95%CI: 4.494-8.256).

CONCLUSION

Pregnant women with normal ferritin or SI levels and iron supplements could significantly increase the risks for GDM.

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

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.

Impaired pancreatic beta-cell function after a single dose of oral iron: a before-and-after (pre-post) study

INTRODUCTION

Although in vitro and animal studies have shown that iron loading in pancreatic beta-cells impaired insulin secretion, no human studies have documented the acute effects of oral iron on beta-cell insulin secretory capacity. In this study, we determined beta-cell insulin secretory capacity at baseline and after a single oral dose of iron (ferrous sulphate, 120 mg elemental iron) in healthy male individuals.

METHODS

Fifteen healthy male volunteers underwent an oral glucose tolerance test (OGTT) to document baseline glucose tolerance and insulin secretion kinetics (baseline OGTT). One week later, the same subjects underwent a second OGTT, two hours after an oral dose of ferrous sulfate (120 mg of elemental iron) (post-iron OGTT). Changes in disposition index, insulin secretion kinetics, glucose tolerance, insulin resistance, insulin clearance, and iron-related parameters in serum were determined.

RESULTS

Compared to baseline OGTT, the areas under the curve (AUC) for serum iron and transferrin saturation increased by 125% and 118% respectively, in the post-iron OGTT. The disposition index decreased by 20% (p=0.009) and the AUC for glucose concentrations increased by 5.7% (p<0.001) during the post-iron OGTT. The insulin secretion rate was marginally lower during the first hour (-3.5%, p=0.63), but became significantly higher during the second hour (22%, p=0.005) of the post-iron OGTT. Insulin resistance and insulin clearance rate were not affected by iron intake.

CONCLUSION

The decrease in disposition index and glucose tolerance observed after the oral dose of iron points to an acute iron-induced impairment in pancreatic beta-cell insulin secretory capacity. This article is protected by copyright. All rights reserved.

Nutrition as Prevention Factor of Gestational Diabetes Mellitus: A Narrative Review

Gestational diabetes mellitus (GDM) is defined as a glucose tolerance disorder with onset or first recognition during pregnancy. GDM is associated with several adverse maternal and neonatal outcomes. Management to reduce the incidence of GDM could decrease the incidence of these complications. Modification of nutrition in the prevention of GDM is postulated. The vital issue in GDM prevention is the implementation of proper dietary patterns, appropriate physical activity, and a combination of diet and lifestyle modifications. However, intervention studies examining the effects of diet and lifestyle on GDM prevention are contradictory. The aim of this study was to review the scientific evidence on nutritional prevention strategies, including diet and supplementation of some substances such as probiotics, micro/macroelements, fiber, myoinositol, and vitamins that may be effective in reducing the risk of GDM. The presented article is a narrative review. This article indicates that certain nutritional factors may have some benefit in preventing GDM. However, further studies in a variety of populations and large groups of patients are needed. At present, no definitive conclusions can be drawn as to the best intervention in the prevention of GDM.

Association between maternal plasma ferritin concentration, iron supplement use, and the risk of gestational diabetes: a prospective cohort study

BACKGROUND

The association between iron supplementation and gestational diabetes mellitus (GDM) is still inconclusive, and this association has not been extensively studied in relation to plasma ferritin in the early second trimester.

OBJECTIVES

We aimed to prospectively examine the independent and combined associations of plasma ferritin concentrations and iron supplement use with GDM.

METHODS

We studied 2117 women from the Tongji Maternal and Child Health Cohort in Wuhan, China. Plasma ferritin around 16 weeks' gestation was measured by ELISA kits and information on iron supplement use was collected by questionnaires. GDM was diagnosed by a 75-g oral-glucose-tolerance test (OGTT) at 24-28 weeks' gestation. A log-Poisson regression model was used to estimate the RR of GDM associated with plasma ferritin and iron supplementation.

RESULTS

The median and IQR of plasma ferritin was 52.1 (29.6-89.9) ng/mL, and 863 (40.8%) participants reported use of iron supplements during the second trimester. A total of 219 (10.3%) participants developed GDM. Adjusted RRs (95% CIs) for GDM across increasing quartiles of plasma ferritin were 1.00 (reference), 2.14 (1.37, 3.34), 2.03 (1.30, 3.19), and 2.72 (1.76, 4.21), respectively. After adjustment, supplemental iron ≥60 mg/d during the second trimester was associated with an increased risk of GDM compared with nonusers (RR: 1.37; 95% CI: 1.02, 1.84).

CONCLUSIONS

Both elevated plasma ferritin concentrations in the early second trimester and use of ≥60 mg/d of supplemental iron during pregnancy are independently associated with increased risk of GDM. Further clinical trials with precision nutrition approaches considering both baseline iron status and supplement use are needed to evaluate the benefits and risks of iron supplementation during pregnancy.

Periconceptional iron supplementation and risk of gestational diabetes mellitus: A prospective cohort study

AIMS

Iron supplementation has been recommended for healthy pregnancy, but concerns have been raised regarding the potential adverse effects. We sought to examine the impact of periconceptional iron supplement use on subsequent gestational diabetes mellitus (GDM) risk.

METHODS

Participants (N = 5101) with information on periconceptional micronutrient supplementation and diagnosis of GDM were involved. Information on iron supplementation and general characteristics were collected at enrollment and follow-up visits. GDM was diagnosed by oral glucose tolerance tests (OGTT) conducted at 24-28 weeks of gestation. Robust Poisson regression model was used to estimate the relative risks (RRs) and 95% confidence intervals (CI) for the effect of iron supplement use on GDM.

RESULTS

10.5% of the participants were diagnosed with GDM and the incidence was significantly higher in users with iron >30 mg/d for more than 3 months (Iron >30-L) than in nonusers. Adjusted RRs (95% CI) were 1.53 (1.21, 1.93) in Iron >30-L group, 1.14 (0.80, 1.61) in users with iron >30 mg/d for<3 months (Iron > 30-S) and 1.15 (0.86, 1.54) in users with iron ≤30 mg/d for any duration (Iron ≤30) respectively, compared to nonusers. This link in Iron >30-L group was even stronger (adjusted RR: 1.70, 95% CI: 1.25, 2.31) when restricting the analysis among primiparous and iron-replete participants without family history of diabetes. There were no significant differences in birth outcomes among groups.

CONCLUSIONS

Periconceptional iron supplementation >30 mg/d for long-term was associated with increased GDM risk. The need and safety of prophylactic iron supplement in iron-replete pregnant women should be reconsidered.

Hemoglobin concentration and iron supplement during pregnancy were associated with an increased risk of gestational diabetes mellitus

BACKGROUND

Hemoglobin (Hb) measurement is a conventional test during perinatal visits. Hb concentration is related to iron supplement. However, studies focusing on Hb levels, iron supplement, and pregnancy outcomes are scarce. This study aimed to determine whether Hb levels and iron supplement were associated with the risk of gestational diabetes mellitus (GDM).

METHODS

A running hospital-based cohort was conducted from August, 2011. The demographic data and medical information were collected individually through questionnaires and patient medical records. Multiple linear regression was applied for the association between Hb levels, iron supplement, and blood glucose. Multiple logistic regression was used for evaluating odds ratios between Hb levels, iron supplement, and GDM.

RESULTS

Hb levels during first (T1) and second trimester (T2) of pregnancy were significantly and positively associated with blood glucose and GDM risk. After adjusting for age, prepregnancy body mass index, and other risk factors, pregnant women with Hb ≥ 11 g/dL and iron supplement had higher postprandial blood glucose at 1 hour (Hb ≥ 11 g/dL in T2 and iron supplement in T1: β = 0.860，P = <0.001; Hb ≥ 11 g/dL in T2 and iron supplement in T2: β = 0.960，P < 0.001; Hb ≥ 11 g/dL in T1 and iron supplement in T2: β = 1.133, P = 0.033) and GDM risks (odds ratio [OR] = 1.53, 95% confidence interval [CI]: 1.05-2.24; OR = 1.92, 95% CI: 1.13-3.35; OR = 2.15, 95% CI: 1.07-4.34, respectively), compared with those with Hb < 11 g/dL and without iron supplement.

CONCLUSION

High Hb concentration and iron supplements without anemia increased postprandial blood glucose and risks for GDM. It indicates that pregnant women with good Hb levels should not be advised to take iron supplements during pregnancy.

Multiple Micronutrient Supplementation during Pregnancy and Increased Birth Weight and Skinfold Thicknesses in the Offspring: The Cambridge Baby Growth Study

Multiple micronutrient supplementation (MMS) in pregnancy has previously been associated with positive effects on fetal growth, but its value in high-income countries remains controversial. In this study, we investigated effects of pregnancy MMS on offspring size at birth and adiposity, along with risks of various maternal outcomes of pregnancy, using the prospective Cambridge Baby Growth Study. Maternal MMS was reported in 528 out of 970 women who completed pregnancy questionnaires. Gestational diabetes (GDM) was assessed using results from 75 g oral glucose tolerance tests at week 28 of pregnancy. Offspring size at birth was assessed using standard anthropometric measurements and adiposity using skinfold calipers. MMS was associated with increased risk of developing GDM (risk ratio = 1.86 (1.13–3.08), p = 0.02), as well as increased offspring size at birth in terms of weight (p = 0.03), head circumference (p = 0.04), and flank, and subscapular and triceps skinfold thicknesses (p = 0.04, 0.03, and 0.003, respectively). There was no association with quadriceps skinfold thickness (p = 0.2), suggesting that the increased adiposity was partially regionalized. In women who underwent oral glucose tolerance testing, nearly all of these associations were attenuated by adjusting for GDM. These results suggest that the increased offspring size at birth, including (regionalized) adiposity associated with pregnancy, and MMS may be partially related to the development of GDM.

Diet and Healthy Lifestyle in the Management of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) among pregnant women increases the risk of both short-term and long-term complications, such as birth complications, babies large for gestational age (LGA), and type 2 diabetes in both mother and offspring. Lifestyle changes are essential in the management of GDM. In this review, we seek to provide an overview of the lifestyle changes which can be recommended in the management of GDM. The diet recommended for women with GDM should contain sufficient macronutrients and micronutrients to support the growth of the foetus and, at the same time, limit postprandial glucose excursions and encourage appropriate maternal gestational weight gain. Blood glucose excursions and hyperglycaemic episodes depend on carbohydrate-intake. Therefore, nutritional counselling should focus on the type, amount, and distribution of carbohydrates in the diet. Further, physical activity has beneficial effects on glucose and insulin levels and it can contribute to a better glycaemic control.

Effect of micronutrient supplements on low-risk pregnancies in high-income countries: a systematic quantitative literature review

OBJECTIVE

To assess the quantity and focus of recent empirical research regarding the effect of micronutrient supplementation on live birth outcomes in low-risk pregnancies from high-income countries.

DESIGN

A systematic quantitative literature review.

SETTING

Low-risk pregnancies in World Bank-classified high-income countries, 2019.

RESULTS

Using carefully selected search criteria, a total of 2475 publications were identified, of which seventeen papers met the inclusion criteria for this review. Data contributing to nine of the studies were sourced from four cohorts; research originated from ten countries. These cohorts exhibited a large number of participants, stable data and a low probability of bias. The most recent empirical data offered by these studies was 2011; the most historical was 1980. In total, fifty-five categorical outcome/supplement combinations were examined; 67·3 % reported no evidence of micronutrient supplementation influencing selected outcomes.

CONCLUSIONS

A coordinated, cohesive and uniform empirical approach to future studies is required to determine what constitutes appropriate, effective and safe micronutrient supplementation in contemporary cohorts from high-income countries, and how this might influence pregnancy outcomes.

Gestational diabetes mellitus affects placental iron homeostasis: Mechanism and clinical implications

Clinical studies suggest that pregnant women with elevated iron levels are more vulnerable to develop gestational diabetes mellitus (GDM), but the causes and underlying mechanisms are unknown. We hypothesized that hyperglycemia induces cellular stress responses leading to dysregulated placental iron homeostasis. Hence, we compared the expression of genes/proteins involved in iron homeostasis in placentae from GDM and healthy pregnancies (n = 11 each). RT-qPCR and LC-MS/MS analyses revealed differential regulation of iron transporters/receptors (DMT1/FPN1/ZIP8/TfR1), iron sensors (IRP1), iron regulators (HEPC), and iron oxidoreductases (HEPH/Zp). To identify the underlying mechanisms, we adapted BeWo trophoblast cells to normoglycemic (N), hyperglycemic (H), and hyperglycemic-hyperlipidemic (HL) conditions and assessed Fe³⁺ -uptake, expression patterns, and cellular pathways involving oxidative stress (OS), ER-stress, and autophagy. H and HL induced alterations in cellular morphology, differential iron transporter expression, and reduced Fe³⁺ -uptake confirming the impact of hyperglycemia on iron transport observed in GDM patients. Pathway analysis and rescue experiments indicated that dysregulated OS and disturbed autophagy processes contribute to the reduced placental iron transport under hyperglycemic conditions. These adaptations could represent a protective mechanism preventing the oxidative damage for both fetus and placenta caused by highly oxidative iron. In pregnancies with risk for GDM, antioxidant treatment, and controlled iron supplementation could help to balance placental OS levels protecting mother and fetus from impaired iron homeostasis.

Influence of selenium supplementation on carbohydrate metabolism and oxidative stress in pregnant women with gestational diabetes mellitus

BACKGROUND

In the presence of conflicting advice about the relationship between selenium-type II diabetes-oxidative stress trio, this study aimed to assess the consequences of selenium supplementation on fasting plasma glucose (FPG) level, antioxidant activities of selenodependent and non-selenodependent enzymes, and other markers of oxidative stress studied for the first time during gestational diabetes mellitus (GDM).

METHODS

This research was carried out among 180 pregnant Algerian women, 60 of whom were in good health, 60 women with GDM did not take supplements, and 60 women with GDM took selenium orally (50 mg/d) for 12 weeks starting from their second trimester of pregnancy. Blood samples were taken in order to assay FPG level and oxidative stress markers.

RESULTS

Selenium supplementation during GDM has demonstrated its hypoglycemic power in the significant decline of FPG level, and its antioxidant properties in the significant reinforcement of antioxidant activities of erythrocyte selenodependent enzymes (glutathione peroxidase and glutathione reductase), the significant increase in erythrocyte catalase and superoxide dismutase activities simultaneously with the highest decrease in erythrocyte and plasma malondialdehyde levels. This decrease was only significant for plasma carbonyl proteins, which was not the case for erythrocyte carbonyl proteins.

CONCLUSIONS

The recourse to selenium supplementation by seleno-deficient pregnant women with GDM is beneficial for maternal health. This micronutrient exploits its antioxidant and insulin-mimetic properties in the maintenance of blood glucose homeostasis and the fight against oxidative stress, and consequently, its supplementation delays the occurrence of GDM complications.

Iron-Related Factors in Early Pregnancy and Subsequent Risk of Gestational Diabetes Mellitus: the Ma'anshan Birth Cohort (MABC) Study

Iron is an essential micronutrient while its excessive load has been related to the etiology of diabetes. We used data of 3289 pregnant women from the Ma'anshan birth cohort (MABC) study in China to examine the associations of three iron-related factors (i.e., serum iron (SI) concentration, hemoglobin level, and use of iron supplements) with risk of gestational diabetes mellitus (GDM). Emphatically explore the potential non-linear relationship between SI concentration and risk of GDM. SI concentration was measured in fasting blood using inductively coupled plasma mass spectrometry (ICP-MS). GDM diagnosis was determined by 75 g oral glucose tolerance test at 24~28 weeks. Restricted cubic splines with three knots were used to examine potential non-linear relationship between SI concentration and GDM risk. We observed a U-shape relation between SI concentration in the first trimester and risk of GDM. In the multivariate-adjusted model, compared with the middle level (ln(SI), 7.1-7.7 μg/L), both the lowest level (ln(SI) ≤ 7.1 μg/L) (odds ratio (OR) = 1.35, 95% confidence interval (CI) = 1.04-1.76) and the highest level (ln(SI) > 7.7 μg/L) (OR = 1.63, 95%CI = 1.16-2.28) increased risk of GDM. Associations of hemoglobin level in the first trimester and risk of GDM attenuated to non-significance after adjustment for pre-pregnancy body mass index (BMI) and blood pressure. Pre-pregnancy iron supplement use was associated with an increased risk of GDM (OR = 1.57, 95%CI = 1.06-2.32). In conclusion, the three iron-related factors are all related to GDM risk on some level.

The use of folic acid, iron salts and other vitamins by pregnant women in the 2015 Pelotas birth cohort: is there socioeconomic inequality?

BACKGROUND

Many low- and middle-income countries recommend micronutrient supplements for pregnant women to improve their nutritional status, prevent possible deficiencies and avoid fetal healgth consequences. This study evaluated the influence of socioeconomic status on the use of folic acid, iron salts and other vitamins and minerals among pregnant women in the 2015 Pelotas Birth Cohort.

METHODS

This population-based birth cohort study was carried out with 4270 women. Participants were interviewed during pregnancy and at the maternity hospital about the antenatal period; including the use of iron salts, vitamins and other minerals. Descriptive analyses were performed to characterize the sample. The analyses were adjusted according to socioeconomic variables (maternal education, ethnicity, household income).

RESULTS

The overall prevalence of the use of folic acid, iron salts or other vitamins and minerals was 91.0% (95% CI: 90.1-91.8). Specifically, 70.9% (95% CI: 69.5-72.3) used folic acid, 72.9% (95% CI: 71.5-74.3) used iron compounds, and 31.8% (95% CI: 30.3-33.2) used other vitamins or minerals. In the adjusted analysis, the use of iron salts was associated with nonwhite mothers, with ≤4 years of education and whose family income was less than or equal to the monthly minimum wage. The use of folic acid and other vitamins and minerals was associated with white mothers who were more highly educated and had a higher family income.

CONCLUSION

Although folic acid and other vitamins and minerals were more frequently used in white, richer and more educated mothers, which indicates inequality, iron supplements were more frequently used in the poorer, less educated nonwhite mothers, suggesting the opposite association for this supplement.

Association of maternal iron deficiency anemia with the risk of gestational diabetes mellitus: a meta-analysis

PURPOSE

The aim of the study was to conduct a meta-analysis investigating the association of maternal iron deficiency anemia (IDA) and risk of gestational diabetes mellitus (GDM).

METHODS

Literature search was conducted in various database websites such as PubMed, Cochrane Library, and Web of Science up to 17 June 2018 for related publications written in English. Selected data were extracted from the included studies and were subjected to statistical analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed, pooled, and interpreted. Subgroup analysis by ethnicity (Asians vs. Caucasians) was also performed.

RESULTS

Six studies with a total sample size of 15,157 from various countries were included in this meta-analysis. Pooled ORs of all publications included show that pregnant women with IDA have a reduced risk of developing GDM (OR 0.61; 95% CI 0.47-0.80; P^A = 0.0003). Subgroup analysis, on the other hand, showed significant associations among Asians (OR 0.60; 95% CI 0.45-0.79; P^A = 0.0003) than Caucasians (OR 0.76; 95% CI 0.32-1.76; P^A = 0.52).

CONCLUSION

Results of this meta-analysis suggests that pregnant women with IDA are 39% less likely to develop GDM. However, more studies are needed to confirm the claims of our results.

Gestational diabetes mellitus is associated with increased CD163 expression and iron storage in the placenta

PROBLEM

GDM has been associated with disturbances in iron homeostasis and exaggerated immune activation. We sought to investigate the extent to which placental iron storage and macrophage accumulations were altered in GDM.

METHOD OF STUDY

We conducted a retrospective, case-control study of archived placental tissues obtained from 22 pregnancies complicated by GDM and 22 unaffected controls. Controls were matched to cases based on maternal age, gestational age at birth, and method of delivery. Placental tissues were assessed for altered histology and CD68 and CD163 staining. Tissue iron was assessed using Prussian blue staining.

RESULTS

Maternal hematocrit levels were higher in GDM participants compared to controls (P = 0.02). The presence of meconium-laden macrophages was significantly greater within the amnion of GDM cases (adjusted odds ratio (OR) 12.51). Although the total abundance of CD68-expressing macrophages was not significantly different between groups, we detected a significantly greater abundance of CD163 expression within the chorion and decidua of cases. The total area staining positive for iron was 24% (95% confidence intervals of 2%-46%) greater in GDM placentae versus controls.

CONCLUSION

GDM is associated with altered placental histology and increases in meconium-laden macrophages. Greater iron stores within the placentae of women with GDM is consistent with reports that iron excess is associated with an increased risk for GDM. The higher level of expression of CD163 on macrophage-like cells of the chorion and decidua in GDM suggests an increase in M2-like macrophages. Overall, our results add to growing evidence that GDM has direct effects on placental structure.

Iron Status and Gestational Diabetes-A Meta-Analysis

A meta-analysis of the association of iron overload with gestational diabetes mellitus (GDM) may inform the health debate. We performed a meta-analysis investigating the association of iron biomarkers and dietary iron exposure with GDM. We identified 33 eligible studies (N = 44,110) published in 2001–2017. The standardized mean differences (SMD) in women who had GDM compared to pregnant women without were 0.25 µg/dL (95% CI: 0.001–0.50) for iron, 1.54 ng/mL (0.56–2.53) for ferritin, 1.05% (0.02 to 2.08) for transferrin saturation, and 0.81 g/dL (0.40–1.22) for hemoglobin. Adjusted odds ratio for GDM were 1.58 (95% CI: 1.20–2.08) for ferritin, 1.30 (1.01–1.67) for hemoglobin, and 1.48 (1.29–1.69) for dietary heme intake. We did not find any differences in TIBC or transferrin concentration in women with and without GDM. We also did not find any association of increased transferrin receptor or increased intake of total dietary iron, non-heme iron or supplemental iron, with increased odds ratios for GDM. Considerable heterogeneity was present among the studies (0–99%), but no evidence of publication bias. Accumulating evidence suggests that circulating and dietary iron biomarkers among pregnant women are associated with GDM, but the results should be interpreted with caution due to the high heterogeneity of analyses. Randomized trials investigating the benefits of iron reduction in women at high risk for GDM are warranted.

Integrating themes, evidence gaps, and research needs identified by workshop on iron screening and supplementation in iron-replete pregnant women and young children

This report addresses the evidence and the uncertainties, knowledge gaps, and research needs identified by participants at the NIH workshop related to iron screening and routine iron supplementation of largely iron-replete pregnant women and young children (6-24 mo) in developed countries. The workshop presentations and panel discussions focused on current understanding and knowledge gaps related to iron homeostasis, measurement of and evidence for iron status, and emerging concerns about supplementing iron-replete members of these vulnerable populations. Four integrating themes emerged across workshop presentations and discussion and centered on 1) physiologic or developmental adaptations of iron homeostasis to pregnancy and early infancy, respectively, and their implications, 2) improvement of the assessment of iron status across the full continuum from iron deficiency anemia to iron deficiency to iron replete to iron excess, 3) the linkage of iron status with health outcomes beyond hematologic outcomes, and 4) the balance of benefit and harm of iron supplementation of iron-replete pregnant women and young children. Research that addresses these themes in the context of the full continuum of iron status is needed to inform approaches to the balancing of benefits and harms of screening and routine supplementation.

Dietary iron intake, iron status, and gestational diabetes

Pregnant women are particularly vulnerable to iron deficiency and related adverse pregnancy outcomes and, as such, are routinely recommended for iron supplementation. Emerging evidence from both animal and population-based studies, however, has raised potential concerns because significant associations have been observed between greater iron stores and disturbances in glucose metabolism, including increased risk of type 2 diabetes among nonpregnant individuals. Yet, the evidence is uncertain regarding the role of iron in the development of gestational diabetes mellitus (GDM), a common pregnancy complication which has short-term and long-term adverse health ramifications for both women and their children. In this review, we critically and systematically evaluate available data examining the risk of GDM associated with dietary iron, iron supplementation, and iron status as measured by blood concentrations of several indicators. We also discuss major methodologic concerns regarding the available epidemiologic studies on iron and GDM.

Introduction to workshop on iron screening and supplementation in iron-replete pregnant women and young children

The NIH Office of Dietary Supplements convened a public workshop on iron screening and supplementation in iron-replete pregnant women and young children in 2016 in Bethesda, Maryland. The starting point for the workshop was the recent reports from the US Preventive Services Task Force concluding that there was insufficient evidence to evaluate the benefits and harms associated with iron screening and routine supplementation among asymptomatic pregnant women and young children (6-24 mo old) in the United States. The goal of the workshop was to explore and refine understanding about the existing knowledge gaps and research needs associated with these preventive services for these groups. Given the focus on the United States, planning for the workshop took into account the higher iron status in the United States compared with developing countries and, in turn, included a focus on iron-replete individuals consistent with the U-shaped risk curve for nutrient-health relations. Topic areas included adaptations in iron homeostasis associated with pregnancy and young childhood, the impact of inflammation, measurement of iron status, current estimates of iron status for pregnant women and young children in the United States and in Europe, and emerging evidence suggesting adverse effects associated with iron supplementation of iron-replete individuals. A crosscutting dialogue conducted at the close of the workshop formed the basis for a workshop summary that specified evidence gaps and research needs in a range of areas centered on the relation of these adaptations of iron homeostasis with the response to and risk from iron supplementation as well as the need for indicators informative of the full continuum of iron status and based on health outcomes, not just erythropoiesis.

Incidence and progression of diabetic retinopathy in Sub-Saharan Africa: A five year cohort study

Aims

To describe the incidence and progression of retinopathy in people with diabetes in Southern Malawi over 5 years. To document visual loss in a setting where laser treatment is not available.

Methods

Subjects from a cohort sampled from a hospital-based, primary-care diabetes clinic in 2007 were traced in 2012. Laser treatment was not available. Modified Wisconsin grading of retinopathy was performed using slit lamp biomicroscopy by a single ophthalmologist in 2007 and using four-field mydriatic fundus photographs at an accredited reading centre in 2012. Visual acuity was measured by Snellen chart in 2007 and by ‘Early Treatment of Diabetic Retinopathy Study’ chart in 2012. HbA1c, blood pressure, HIV status, urine albumin–creatinine ratio, haemoglobin and lipids were measured.

Results

Of 281 subjects recruited in 2007, 135 (48%) were traced and assessed, 15 were confirmed dead. At follow-up (median 5.3 years) ≥2 step retinopathy progression was observed in 48 subjects (36.4%; 95% CI 28.2–44.6). Incidence of sight threatening diabetic retinopathy for those with level 10 (no retinopathy) and level 20 (background) retinopathy at baseline, was 19.4% (11.3–27.4) and 81.3% (62.1–100), respectively. In multivariate analysis 2 step progression was associated with HbA1c (OR 1.2495%CI 1.04–1.48), and haemoglobin level (0.77, 0.62–0.98). 25 subjects (18.8%) lost ≥5 letters, 7 (5.3%) lost ≥15 letters.

Conclusions

Progression to sight threatening diabetic retinopathy from no retinopathy and background retinopathy was approximately 5 and 3 times that reported in recent European studies, respectively. Incidence of visual loss was high in a location where treatment was not available.

Association between pre-pregnancy consumption of meat, iron intake, and the risk of gestational diabetes: the SUN project

PURPOSE

We assessed the association of total meat, processed, and unprocessed red meat and iron intake with the risk of developing gestational diabetes mellitus (GDM) in pregnant women.

METHODS

We conducted a prospective study among 3298 disease-free Spanish women participants of the SUN cohort who reported at least one pregnancy between December 1999 and March 2012. Meat consumption and iron intake were assessed at baseline through a validated, 136-item semi-quantitative, food frequency questionnaire. We categorized total, red, and processed meat consumption and iron intake into quartiles. Logistic regression models were used to adjust for potential confounders.

RESULTS

We identified 172 incident cases of GDM. In the fully adjusted analysis, total meat consumption was significantly associated with a higher risk of GDM [OR = 1.67 (95% CI 1.06-2.63, p-trend 0.010)] for the highest versus the lowest quartile of consumption. The observed associations were particularly strong for red meat consumption [OR = 2.37 (95% CI 1.49-3.78, p-trend < 0.001)] and processed meat consumption [OR = 2.01 (95% CI 1.26-3.21, p-trend 0.003)]. Heme iron intake was also directly associated with GDM [OR = 2.21 (95% CI 1.37-3.58, p-trend 0.003)], although the association was attenuated and lost its statistical significance when we adjusted for red meat consumption [OR = 1.57 (95% CI 0.91-2.70, p-trend 0.213)]. No association was observed for non-heme and total iron intake, including supplements.

CONCLUSIONS

Our overall findings suggest that higher pre-pregnancy consumption of total meat, especially red and processed meat, and heme iron intake, are significantly associated with an increased GDM risk in a Mediterranean cohort of university graduates.

First Prospective Cohort Study of Diabetic Retinopathy from Sub-Saharan Africa: High Incidence and Progression of Retinopathy and Relationship to Human Immunodeficiency Virus Infection

PURPOSE

To describe the prevalence, incidence, and progression of retinopathy and to report associations with demographic, clinical, and biochemical variables in people with diabetes in Southern Malawi.

DESIGN

Prospective cohort study.

PARTICIPANTS

Subjects were systematically sampled from 2 primary care diabetes clinics.

METHODS

We performed the first prospective cohort study of diabetic retinopathy from Sub-Saharan Africa over 24 months. Visual acuity, glycemic control, blood pressure, human immunodeficiency virus (HIV) status, urine albumin-to-creatinine ratio, hemoglobin, and lipids were assessed. Retinopathy was graded at an accredited reading center using modified Wisconsin grading of 4-field mydriatic photographs.

MAIN OUTCOME MEASURES

Incidence of sight-threatening retinopathy and progression of retinopathy by 2 steps on the Liverpool Diabetic Eye Study Scale.

RESULTS

A total of 357 subjects were recruited to the 24-month cohort study. At baseline, 13.4% of subjects were HIV positive and 15.1% were anemic. The 2-year incidence of sight-threatening diabetic retinopathy (STDR) for subjects with level 10 (no retinopathy), level 20 (background), and level 30 (preproliferative) retinopathy at baseline was 2.7% (95% confidence interval [CI], 0.1-5.3), 27.3% (95% CI, 16.4-38.2), and 25.0% (95% CI, 0-67.4), respectively. In a multivariate logistic analysis, 2-step progression of diabetic retinopathy was associated with glycosylated hemoglobin (odds ratio [OR], 1.27; 95% CI, 1.12-1.45), baseline grade of retinopathy (OR, 1.39; 95% CI, 1.02-1.91), and HIV infection (OR, 0.16; 95% CI, 0.03-0.78). At 2 years, 17 subjects (5.8%) lost ≥15 letters.

CONCLUSIONS

Incidence of STDR was approximately 3 times that reported in recent European studies. The negative association of HIV infection with retinopathy progression is a new finding.

Preconceptional Iron Intake and Gestational Diabetes Mellitus

Our objective was to assess the impact of preconceptional heme and non-heme iron on gestational diabetes mellitius (GDM) in the Boston University Slone Epidemiology Birth Defects Study (BDS). This retrospective cohort analysis included 7229 participants enrolled in the BDS between 1998 and 2008 who gave birth to non-malformed infants and were free of pre-existing diabetes. All data were collected through structured interviews conducted within 6 months of delivery. Calorie-adjusted and multivariable odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression models. Preconceptional dietary heme iron was modestly associated with an elevated risk of GDM among those (multivariable OR comparing the fifth quintile to the first: 1.55; 95% CI 0.98, 2.46). Conversely, preconceptional dietary non-heme iron was associated with a decreased risk of GDM among those in the fifth quintile of intake compared to the first (multivariable OR: 0.48; 95% CI 0.28, 0.81). Women who consumed supplemental iron during preconception also had a decreased risk of GDM (multivariable OR: 0.78; 95% CI 0.60, 1.02). In conclusion, our data support a positive association between preconceptional heme iron intake and GDM and an inverse association between preconceptional non-heme iron intake from foods and preconceptional intake from supplements.

Beta Cell Function and the Nutritional State: Dietary Factors that Influence Insulin Secretion

Approximately 366 million people worldwide have been diagnosed with type-2 diabetes (T2D). Chronic insulin resistance, decreased functional β-cell mass, and elevated blood glucose are defining characteristics of T2D. Great advances have been made in understanding the pathogenesis of T2D with respect to the effects of dietary macronutrient composition and energy intake on β-cell physiology and glucose homeostasis. It has been further established that obesity is a leading pathogenic factor for developing insulin resistance. However, insulin resistance may not progress to T2D unless β-cells are unable to secret an adequate amount of insulin to compensate for decreased insulin sensitivity. Therefore, pancreatic β-cell dysfunction plays an important role in the development of overt diabetes. This paper reviews recent research findings on the effects of several micronutrients (zinc, vitamin D, iron, vitamin A), leucine, and the phytochemical, genistein on pancreatic β-cell physiology with emphasis on their effects on insulin secretion, specifically in the context of T2D.

Iron, oxidative stress and gestational diabetes

Both iron deficiency and hyperglycemia are highly prevalent globally for pregnant women. Iron supplementation is recommended during pregnancy to control iron deficiency. The purposes of the review are to assess the oxidative effects of iron supplementation and the potential relationship between iron nutrition and gestational diabetes. High doses of iron (~relative to 60 mg or more daily for adult humans) can induce lipid peroxidation in vitro and in animal studies. Pharmaceutical doses of iron supplements (e.g., 10× RDA or more for oral supplements or direct iron supplementation via injection or addition to the cell culture medium) for a short or long duration will induce DNA damage. Higher heme-iron intake or iron status measured by various biomarkers, especially serum ferritin, might contribute to greater risk of gestational diabetes, which may be mediated by iron oxidative stress though lipid oxidation and/or DNA damage. However, information is lacking about the effect of low dose iron supplementation (≤60 mg daily) on lipid peroxidation, DNA damage and gestational diabetes. Randomized trials of low-dose iron supplementation (≤60 mg daily) for pregnant women are warranted to test the relationship between iron oxidative stress and insulin resistance/gestational diabetes, especially for iron-replete women.

Evidence that multiple defects in lipid regulation occur before hyperglycemia during the prodrome of type-2 diabetes

BACKGROUND

Blood-vessel dysfunction arises before overt hyperglycemia in type-2 diabetes (T2DM). We hypothesised that a metabolomic approach might identify metabolites/pathways perturbed in this pre-hyperglycemic phase. To test this hypothesis and for specific metabolite hypothesis generation, serum metabolic profiling was performed in young women at increased, intermediate and low risk of subsequent T2DM.

METHODS

Participants were stratified by glucose tolerance during a previous index pregnancy into three risk-groups: overt gestational diabetes (GDM; n = 18); those with glucose values in the upper quartile but below GDM levels (UQ group; n = 45); and controls (n = 43, below the median glucose values). Follow-up serum samples were collected at a mean 22 months postnatally. Samples were analysed in a random order using Ultra Performance Liquid Chromatography coupled to an electrospray hybrid LTQ-Orbitrap mass spectrometer. Statistical analysis included principal component (PCA) and multivariate methods.

FINDINGS

Significant between-group differences were observed at follow-up in waist circumference (86, 95%CI (79-91) vs 80 (76-84) cm for GDM vs controls, p<0.05), adiponectin (about 33% lower in GDM group, p = 0.004), fasting glucose, post-prandial glucose and HbA1c, but the latter 3 all remained within the 'normal' range. Substantial differences in metabolite profiles were apparent between the 2 'at-risk' groups and controls, particularly in concentrations of phospholipids (4 metabolites with p ≤ 0.01), acylcarnitines (3 with p ≤ 0.02), short- and long-chain fatty acids (3 with p<  = 0.03), and diglycerides (4 with p ≤ 0.05).

INTERPRETATION

Defects in adipocyte function from excess energy storage as relatively hypoxic visceral and hepatic fat, and impaired mitochondrial fatty acid oxidation may initiate the observed perturbations in lipid metabolism. Together with evidence from the failure of glucose-directed treatments to improve cardiovascular outcomes, these data and those of others indicate that a new, quite different definition of type-2 diabetes is required. This definition would incorporate disturbed lipid metabolism prior to hyperglycemia.

Supplemental iron intake and the risk of glucose intolerance in pregnancy: re-analysis of a randomised controlled trial in Finland

Observational studies suggest that high iron intake during pregnancy is associated with the risk of gestational diabetes. As such studies are prone to bias, we re-analysed data from a randomised controlled trial of iron supplementation to see whether it supports the risk found in observational studies. The trial was conducted in primary health care setting in five municipalities in Finland in 1985-1986. The participants were 2944 women (95% of pregnant women in the area) who were randomly allocated either to (1) the selective iron group (elemental iron 50 mg twice a day only if diagnosed as anaemic, continuing until their haemoglobin increased to 110 g L(-1)) or (2) the routine iron group (elemental iron 100 mg day(-1) throughout the pregnancy regardless of haemoglobin level). The numbers of women in the analyses were 1358 and 1336, respectively. The main outcome measure was a composite variable including any glucose intolerance-related outcome (e.g. glucosuria, gestational diabetes, large-for-gestational-age child) in mothers' or children's patient records during pregnancy and post-partum. There were no statistically significant differences in the incidence of the primary outcome between the selective iron and the routine iron groups (13.0 vs. 11.0%, P = 0.12). The most common outcome was large-for-gestational-age calculated from children's hospital data (8.3 vs. 8.2%, P = 0.95). The results were mainly similar when stratified by the mothers' baseline haemoglobin level, body mass index or gestational weight gain. Routine iron supplementation throughout pregnancy did not increase the risk of glucose intolerance during pregnancy. The results need to be confirmed in future trials.

Epidemiological associations between iron and cardiovascular disease and diabetes

Disruptions in iron homeostasis are linked to a broad spectrum of chronic conditions including cardiovascular, malignant, metabolic, and neurodegenerative disease. Evidence supporting this contention derives from a variety of analytical approaches, ranging from molecular to population-based studies. This review focuses on key epidemiological studies that assess the relationship between body iron status and chronic diseases, with particular emphasis on atherosclerosis ,metabolic syndrome and diabetes. Multiple surrogates have been used to measure body iron status, including serum ferritin, transferrin saturation, serum iron, and dietary iron intake. The lack of a uniform and standardized means of assessing body iron status has limited the precision of epidemiological associations. Intervention studies using depletion of iron to alter risk have been conducted. Genetic and molecular techniques have helped to explicate the biochemistry of iron metabolism at the molecular level. Plausible explanations for how iron contributes to the pathogenesis of these chronic diseases are beginning to be elucidated. Most evidence supports the hypothesis that excess iron contributes to chronic disease by fostering excess production of free radicals. Overall, epidemiological studies, reinforced by basic science experiments, provide a strong line of evidence supporting the association between iron and elevated risk of cardiovascular disease and diabetes. In this narrative review we attempt to condense the information from existing literature on this topic.

Is oxidative stress induced by iron status associated with gestational diabetes mellitus?

Gestational diabetes mellitus (GDM) is a common pregnancy complication in high risk populations, and is associated with increased perinatal and long term outcomes for both mothers and newborns. Both its prevention and early management can be reinforced by identifying risks factors, particularly those factors influencing glucose metabolism. On the other hand, several epidemiological studies have shown an increased oxidative stress (OS) in pregnant women with GDM. Elevated OS was also reported in pregnant women supplemented with iron, which can generate OS and may also influence insulin resistance. This review summarizes the current state of knowledge, highlighting the potential relationship between OS induced by iron status and the development of GDM.

Iron, human growth, and the global epidemic of obesity

Iron is an essential nutrient utilized in almost every aspect of cell function and its availability has previously limited life. Those same properties which allow iron to function as a catalyst in the reactions of life also present a threat via generation of oxygen-based free radicals. Accordingly; life exists at the interface of iron-deficiency and iron-sufficiency. We propose that: (1) human life is no longer positioned at the limits of iron availability following several decades of fortification and supplementation and there is now an overabundance of the metal among individuals of many societies; (2) this increased iron availability exerts a positive effect on growth by targeting molecules critical in regulating the progression of the cell cycle; there is increased growth in humans provided greater amounts of this metal; and indices of obesity can positively correlate with body stores of iron; and (3) diseases of obesity reflect this over-abundance of iron. Testing potential associations between iron availability and both obesity and obesity-related diseases in populations will be difficult since fortification and supplementation is so extensively practiced.

A Comparative Study of Relationship between Micronutrients and Gestational Diabetes

In this paper, we studied the relation between the micronutrient and gestational diabetes. Therefore, we measured micronutrient concentration including Ni, Al, Cr, Mg, Fe, Zn, Cu, and Se in serum of women with gestational diabetes between 24 and 28 weeks of gestational age (study group) who had inclusion criteria and comparison with micronutrient levels in normal pregnant women with same gestational age (control group). Results showed that there was no significant difference between the serum micronutrient level (Ni, Al, Cr, Mg, Zn, Cu, Se) in study and control groups except serum level of iron which in serum of gestational diabetic women was lower than normal pregnant women and difference was significant.

Iron intake, haemoglobin and risk of gestational diabetes: a prospective cohort study

OBJECTIVE

To investigate the possible association between total daily iron intake during pregnancy, haemoglobin in early pregnancy and the risk of gestational diabetes mellitus (GDM) in women at increased risk of GDM.

DESIGN

A prospective cohort study (based on a cluster-randomised controlled trial, where the intervention and the usual care groups were combined).

SETTING

Primary healthcare maternity clinics in 14 municipalities in south-western Finland.

PARTICIPANTS

399 Pregnant women who were at increased risk of GDM participated in a GDM prevention trial and were followed throughout pregnancy.

MAIN OUTCOME MEASUREMENTS

The main outcome was GDM diagnosed with oral glucose tolerance test at 26-28 weeks' gestation or based on a diagnosis recorded in the Finnish Medical Birth registry. Data on iron intake was collected using a 181-item food frequency questionnaire and separate questions for supplement use at 26-28 weeks' gestation.

RESULTS

GDM was diagnosed in 72 women (18.1%) in the study population. The OR for total iron intake as a continuous variable was 1.006 (95% CI 1.000 to 1.011; p=0.038) after adjustment for body mass index, age, diabetes in first-degree or second-degree relatives, GDM or macrosomia in earlier pregnancy, total energy intake, dietary fibre, saturated fatty acids and total gestational weight gain. Women in the highest fifth of total daily iron intake had an adjusted OR of 1.66 (95% CI 0.84 to 3.30; p=0.15) for GDM. After excluding participants with low haemoglobin levels (≤120 g/l) already in early pregnancy the adjusted OR was 2.35 (95% CI 1.13 to 4.92; p=0.023).

CONCLUSIONS

Our results suggest that high iron intake during pregnancy increases the risk of GDM especially in women who are not anaemic in early pregnancy and who are at increased risk of GDM. These findings suggest that routine iron supplementation should be reconsidered in this risk group of women.

The role of oxidative stress in the pathophysiology of gestational diabetes mellitus

Normal human pregnancy is considered a state of enhanced oxidative stress. In pregnancy, it plays important roles in embryo development, implantation, placental development and function, fetal development, and labor. However, pathologic pregnancies, including gestational diabetes mellitus (GDM), are associated with a heightened level of oxidative stress, owing to both overproduction of free radicals and/or a defect in the antioxidant defenses. This has important implications on the mother, placental function, and fetal well-being. Animal models of diabetes have confirmed the important role of oxidative stress in the etiology of congenital malformations; the relative immaturity of the antioxidant system facilitates the exposure of embryos and fetuses to the damaging effects of oxidative stress. Of note, there are only a few clinical studies evaluating the potential beneficial effects of antioxidants in GDM. Thus, whether or not increased antioxidant intake can reduce the complications of GDM in both mother and fetus needs to be explored. This review provides an overview and updated data on our current understanding of the complications associated with oxidative changes in GDM.

Micronutrients in pregnancy: current knowledge and unresolved questions

Micronutrient status is increasingly recognized to play an important role in the health and well-being of pregnant women and in the development and long-term health of the offspring. On 26th - 28th February 2009, The Child Health Foundation invited leading experts in this area to a scientific workshop at Obergurgl, Austria to review and critically discuss current knowledge, to identify issues that may need to be addressed in future recommendations, and to highlight priorities and opportunities for future research. This report summarizes updated key conclusions of the workshop with regards to micronutrients' intake and physiological role related to mother, placenta and fetus, as well as relevance for adverse pregnancy and long-term outcomes.

A prospective study of prepregnancy dietary iron intake and risk for gestational diabetes mellitus

OBJECTIVE

It is important to identify modifiable factors that may lower gestational diabetes mellitus (GDM) risk. Dietary iron is of particular interest given that iron is a strong prooxidant, and high body iron levels can damage pancreatic β-cell function and impair glucose metabolism. The current study is to determine if prepregnancy dietary and supplemental iron intakes are associated with the risk of GDM.

RESEARCH DESIGN AND METHODS

A prospective study was conducted among 13,475 women who reported a singleton pregnancy between 1991 and 2001 in the Nurses' Health Study II. A total of 867 incident GDM cases were reported. Pooled logistic regression was used to estimate the relative risk (RR) of GDM by quintiles of iron intake controlling for dietary and nondietary risk factors.

RESULTS

Dietary heme iron intake was positively and significantly associated with GDM risk. After adjusting for age, BMI, and other risk factors, RRs (95% CIs) across increasing quintiles of heme iron were 1.0 (reference), 1.11 (0.87-1.43), 1.31 (1.03-1.68), 1.51 (1.17-1.93), and 1.58 (1.21-2.08), respectively (P for linear trend 0.0001). The multivariate adjusted RR for GDM associated with every 0.5-mg per day of increase in intake was 1.22 (1.10-1.36). No significant associations were observed between total dietary, nonheme, or supplemental iron intake and GDM risk.

CONCLUSIONS

These findings suggest that higher prepregnancy intake of dietary heme iron is associated with an increased GDM risk.

Gestational diabetes mellitus in relation to maternal dietary heme iron and nonheme iron intake

OBJECTIVE

Higher heme iron intake is associated with increased type 2 diabetes risk. However, no previous study has evaluated gestational diabetes mellitus (GDM) risk in relation to heme iron intake during pregnancy. We investigated associations of maternal preconceptional and early pregnancy heme and nonheme iron intake with subsequent GDM risk.

RESEARCH DESIGN AND METHODS

We conducted a prospective cohort study of 3,158 pregnant women. A food frequency questionnaire was used to assess maternal diet. Multivariable generalized linear regression models were used to derive estimates of relative risks (RRs) and 95% CIs.

RESULTS

Approximately 5.0% of the cohort developed GDM (n=158). Heme iron intake was positively and significantly associated with GDM risk (Ptrend=0.04). After adjusting for confounders, women reporting the highest heme iron intake levels (≥1.52 vs. <0.48 mg per day) experienced a 3.31-fold-increased GDM risk (95% CI 1.02-10.72). In fully adjusted models, we noted that a 1-mg per day increase in heme iron was associated with a 51% increased GDM risk (RR 1.51 [95% CI 0.99-2.36]). Nonheme iron was inversely, though not statistically significantly, associated with GDM risk, and the corresponding RRs were 1.00, 0.83, 0.62, and 0.61 across quartiles of nonheme iron intake (Ptrend=0.08).

CONCLUSIONS

High levels of dietary heme iron intake during the preconceptional and early pregnancy period may be associated with increased GDM risk. Associations of GDM risk with dietary nonheme iron intake are less clear. Confirmation of these findings by future studies is warranted.

Critical issues in setting micronutrient recommendations for pregnant women: an insight

The European Micronutrient Recommendations Aligned (EURRECA) Network aims to provide standardized approaches to reveal and beneficially influence variability within the European Union in micronutrient recommendations for vulnerable population groups. Characterization of the 'vulnerability' together with the 'variability' of micronutrient needs represents the first step to creating guidelines for setting micronutrient recommendations within target populations. This paper describes some of the key factors and characteristics relevant to assess micronutrient requirements and formulate recommendations of micronutrients in pregnancy. Nutritional requirements during pregnancy increase to support fetal growth and development as well as maternal metabolism and tissue accretion. Micronutrients are involved in both embryonal and fetal organ development and overall pregnancy outcomes. Several factors may affect directly or indirectly fetal nourishment and the overall pregnancy outcomes, such as the quality of diet including intakes and bioavailability of micronutrients, maternal age, and the overall environment. The bioavailability of micronutrients during pregnancy varies depending on specific metabolic mechanisms because pregnancy is an anabolic and dynamic state orchestrated via hormones acting for both redirection of nutrients to highly specialized maternal tissues and transfer of nutrients to the developing fetus. The timing of prenatal intakes or supplementations of specific micronutrients is also crucial as pregnancy is characterized by different stages that represent a continuum, up to lactation and beyond. Consequently, nutrition during pregnancy might have long-lasting effects on the well-being of the mother and the fetus, and may further influence the health of the baby at a later age.