High maternal iron status, dietary iron intake and iron supplement use in pregnancy and risk of gestational diabetes mellitus: a prospective study and systematic review

Gestational diabetes mellitus is associated with greater incidence of dementia during long-term post-partum follow-up

BACKGROUND

The impact of gestational diabetes mellitus (GDM) on incident dementia is unknown. Our aim was to evaluate the relationship between GDM and all-cause dementia and the mediating effects of chronic diseases on this relationship.

METHODS

This prospective cohort study included women from the UK Biobank who were grouped based on GDM history. Multivariate Cox proportional hazard models were used to explore the associations between GDM and dementia. We further analysed the mediating effects of chronic diseases on this relationship and the interactions of covariates.

RESULTS

A total of 1292 women with and 204,171 women without a history of GDM were included. During a median follow-up period of 45 years after first birth, 2921 women were diagnosed with dementia. Women with a GDM history had a 67% increased risk of incident dementia (hazard ratio 1.67, 95% confidence interval: 1.03-2.69) compared with those without a GDM history. According to mediation analyses, type 2 diabetes, coronary heart disease, chronic kidney disease and comorbidities (diagnosed with any two of the three diseases) explained 34.5%, 8.4%, 5.2% and 18.8% of the mediating effect on the relationship. Subgroup analyses revealed that physical activity modified the association between GDM history and dementia (p for interaction = 0.030). Among physically inactive women, GDM was significantly associated with incident dementia; however, this association was not observed among physically active women.

CONCLUSIONS

A history of GDM was associated with a greater risk of incident dementia. Type 2 diabetes partially mediated this relationship. Strategies for dementia prevention might be considered for women with a history of GDM.

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.

Iron - a background article for the Nordic Nutrition Recommendations 2023

Iron absorption from foods is generally lower than that of most other nutrients and is highly variable depending on individual iron status and iron bioavailability in the meal. Several large population groups in the Nordic and Baltic countries are at risk of iron deficiency, including infants, young children, menstruating females, pregnant women as well as vegetarians. Iron deficiency leads to anemia, fatigue, and limited capacity for physical activity. Of particular concern is that iron deficiency anemia in young children is associated with impaired neurodevelopment. A comprehensive literature search has been performed and summarized. New factorial calculations have been performed considering iron losses, iron absorption and iron requirements in various population groups. Recent data on iron intakes and the prevalence of iron deficiency in the Nordic countries are presented. Average requirements and tentative recommended intakes are presented for 12 different population groups. Pregnant women and those with high menstrual blood losses should consume iron-rich food and undergo screening for iron deficiency. Infants should consume iron-rich complementary foods and cow's milk should be avoided as a drink before 12 months of age and limited to < 500 mL/day in toddlers. Vegetarians should consume a diet including wholegrains, legumes, seeds, and green vegetables together with iron absorption enhancers. There is no evidence that iron intake per se increases the risk of cancer or diabetes. Iron absorption from foods is generally lower than that of most other nutrients and can vary between <2 and 50% depending on individual iron status and iron bioavailability in the meal.

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.

Iron deficiency and iron overload in men and woman of reproductive age, and pregnant women

Iron is an essential micronutrient for human biology and health, but high iron levels can be dangerous. Both iron deficiency and iron overload have been linked to reproductive health. This review summarizes the effects of iron deficiency and iron overload on men of reproductive age, women of reproductive age, and pregnant women. In addition, appropriate iron levels and the need for iron and nutritional supplements at different stages of life and pregnancy are discussed. In general, men should be aware of the risk of iron overload at any stage of life; women should take appropriate iron supplements before menopause; postmenopausal women should pay attention to the risk of iron overload; and pregnant women should receive reasonable iron supplementation in middle and late pregnancy. By summarizing evidence on the relationship between iron and reproductive health, this review aims to promote the development of strategies to optimize reproductive capacity from the perspective of nutrition. However, additional detailed experimental investigations and clinical studies are needed to assess the underlying causes and mechanisms of the observed associations between iron and reproductive health.

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.

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.

Iron Metabolism and Ferroptosis in Physiological and Pathological Pregnancy

Iron is a vital element in nearly every living organism. During pregnancy, optimal iron concentration is essential for both maternal health and fetal development. As the barrier between the mother and fetus, placenta plays a pivotal role in mediating and regulating iron transport. Imbalances in iron metabolism correlate with severe adverse pregnancy outcomes. Like most other nutrients, iron exhibits a U-shaped risk curve. Apart from iron deficiency, iron overload is also dangerous since labile iron can generate reactive oxygen species, which leads to oxidative stress and activates ferroptosis. In this review, we summarized the molecular mechanism and regulation signals of placental iron trafficking under physiological conditions. In addition, we revealed the role of iron metabolism and ferroptosis in the view of preeclampsia and gestational diabetes mellitus, which may bring new insight to the pathogenesis and treatment of pregnancy-related diseases.

Effects of multi-metal exposure on the risk of diabetes mellitus among people aged 40-75 years in rural areas in southwest China

INTRODUCTION

Metals play an important role in diabetes mellitus (DM). This cross-sectional study aims to evaluate the overall, individual, and interactive effects of multi-metal exposure on the prevalence of DM, impaired fasting glucose (IFG) rate, and fasting blood glucose (FBG) levels.

MATERIALS AND METHODS

The FBG levels of a study population from a cadmium (Cd)-polluted area (n=250) and an unpolluted area (n=204) and the metal levels, including magnesium (Mg), calcium (Ca), iron (Fe), zinc (Zn), arsenic (As), Cd, copper (Cu), and lead (Pb), in blood and urine were detected. The study population was divided into a normal fasting glucose (NFG) group, an IFG group, and a DM group on the basis of FBG levels.

RESULTS

IFG rate and DM prevalence were negatively associated with blood Cd and urine Zn levels (IFG rate: OR=0.780, 95%CI: 0.655-0.928; OR=0.622, 95%CI: 0.465-0.831. DM prevalence: OR=0.506, 95%CI: 0.288-0.888; OR=0.609, 95%CI: 0.395-0.939), IFG rate was positively associated with urine Fe levels (OR=1.876, 95%CI: 1.290-2.778), and DM prevalence was positively associated with urine Pb and blood Fe levels (OR=1.185, 95%CI: 1.022-1.376; OR=1.008, 95%CI: 1.001-1.014). A linear negative correlation was observed between FBG levels and blood Cd, and nonlinear inverted U-shaped associations were found between FBG levels and Zn, Pb, and Cu in urine.

CONCLUSIONS

This research suggests that multi-metal exposure, especially Cd, Fe, Zn, Cu, and Pb, is linked to DM, and the interactive effects of multiple metals need further exploration.

Maternal first trimester iron status and its association with obstetric and perinatal outcomes

PURPOSE

To assess the following in singleton pregnant women: (1) associations between first trimester iron deficiency and obstetric and perinatal outcomes, (2) overall first trimester iron status and (3) post-treatment iron status after intensified iron supplementation.

METHODS

A prospective cohort study was conducted with linkage of first trimester hemoglobin and plasma ferritin with obstetric and perinatal data from a hospital database. Blood sample data were obtained from a Danish University Hospital. The cohort was divided into groups according to ferritin and hemoglobin: (1) iron-deficient anemic (ferritin < 30 ng/mL and Hb < 110 g/L), (2) iron-deficient non-anemic (ferritin < 30 ng/mL and Hb ≥ 110 g/L), and (3) iron-replete non-anemic (ferritin 30-200 ng/mL and Hb ≥ 110 g/L). Obstetric and perinatal outcomes in each iron-deficient group were compared to the iron-replete non-anemic group using multivariable logistic regression. The effect of 4 weeks intensified iron supplementation on hemoglobin and ferritin was assessed by groupwise comparisons.

RESULTS

The cohort comprised 5763 singleton pregnant women, of which 14.2% had non-anemic iron deficiency, and 1.2% had iron-deficiency anemia. Compared to iron-replete non-anemic women, iron-deficient anemic women had a higher risk of gestational diabetes (aOR 3.8, 95% CI 1.4-9.0), and iron-deficient non-anemic women had a higher risk of stillbirth (aOR 4.0, 95% CI 1.0-14.3). In group 1 and 2, 81.5% and 67.7% remained iron-deficient after intensified iron supplementation.

CONCLUSION

Iron-deficiency anemia was associated with gestational diabetes, and non-anemic iron deficiency with stillbirth, although risk estimates were imprecise due to few events. Iron deficiency was present in 15.4% and often persisted despite 4 weeks intensified iron supplementation.

Correlation Between High Serum Ferritin Level and Gestational Diabetes: A Systematic Review

Gestational diabetes mellitus (GDM) is a growing pregnancy-related health problem all over the world. It has been noticed that women with high serum ferritin levels have a strong relationship with GDM by increased insulin resistance and increased insulin secretion from the pancreas resulting in pancreatic beta-cell exhaustion. Heme iron is also responsible for increasing the body's iron store and hence causing oxidative injury to pancreatic cells. In this systematic review, we researched the association between high serum ferritin levels and GDM. Three databases were consulted for articles related to GDM and high ferritin. These include Medical Literature Analysis and Retrieval System Online (MEDLINE), PubMed, and PubMed Central (PMC). Additional articles were retrieved from the institutional database. After filtering, 10 articles were finally selected, and quality was checked using the Joanna Briggs Institute (JBI) Critical Appraisal quality check tool. Serum iron biomarkers including ferritin, iron, and soluble transferrin receptor (sTfR) were measured. Our systematic review indicates that high maternal serum ferritin has a significant role in the development of GDM. We have also noticed the importance of sTfR and serum hepcidin as biomarkers to monitor high ferritin levels. Our study also observed a positive relationship between high heme iron intake and gestational diabetes mellitus. Therefore, more research is required to understand this relationship to identify populations at risk.

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.

Associations between Maternal Iron Supplementation in Pregnancy and Changes in Offspring Size at Birth Reflect Those of Multiple Micronutrient Supplementation

It was previously observed that in a population of a high-income country, dietary multiple micronutrient supplementation in pregnancy was associated with an increased risk of gestational diabetes (GDM) and increased offspring size at birth. In this follow-up study, we investigated whether similar changes are observed with dietary iron supplementation. For this we used the prospective Cambridge Baby Growth Study with records of maternal GDM status, nutrient supplementation, and extensive offspring birth size measurements. Maternal iron supplementation in pregnancy was associated with GDM development (risk ratio 1.67 (1.01-2.77), p = 0.048, n = 677) as well as offspring size and adiposity (n = 844-868) at birth in terms of weight (β' = 0.078 (0.024-0.133); p = 0.005), head circumference (β' = 0.060 (0.012-0.107); p = 0.02), body mass index (β' = 0.067 (0.014-0.119); p = 0.01), and various skinfold thicknesses (β' = 0.067-0.094; p = 0.03-0.003). In a subset of participants for whom GDM statuses were available, all these associations were attenuated by adjusting for GDM. Iron supplementation also attenuated the associations between multiple micronutrient supplementation and these same measures. These results suggest that iron supplementation may mediate the effects associated with multiple micronutrient supplementation in pregnancy in a high-income country, possibly through the increased risk of developing GDM.

Iron-dependent apoptosis causes embryotoxicity in inflamed and obese pregnancy

Iron is essential for a healthy pregnancy, and iron supplementation is nearly universally recommended, regardless of maternal iron status. A signal of potential harm is the U-shaped association between maternal ferritin, a marker of iron stores, and risk of adverse pregnancy outcomes. However, ferritin is also induced by inflammation and may overestimate iron stores during inflammation or infection. In this study, we use mouse models to determine whether maternal iron loading, inflammation, or their interaction cause poor pregnancy outcomes. Only maternal exposure to both iron excess and inflammation, but not either condition alone, causes embryo malformations and demise. Maternal iron excess potentiates embryo injury during both LPS-induced acute inflammation and obesity-induced chronic mild inflammation. The adverse interaction depends on TNFα signaling, causes apoptosis of placental and embryo endothelium, and is prevented by anti-TNFα or antioxidant treatment. Our findings raise important questions about the safety of indiscriminate iron supplementation during pregnancy.

Physiological Need for Calcium, Iron, and Folic Acid for Women of Various Subpopulations During Pregnancy and Beyond

Women tend to supplement their diets with multivitamin/mineral (MVM) supplements more often than men, and reports indicate that more than 90% of pregnant women in the United States supplement their diets with prenatal MVMs. Given the widespread use of MVMs among women and given the increasing efforts to unveil the importance of phenotype-specific health determinants, it seems imperative to review what is known about variations in nutrient physiology among women from different ethnic and racial groups and at different reproductive stages of life. In this study, we embark on an assessment of the scientific evidence and knowledge gaps that impact the precise determination of nutrient levels (specifically calcium, iron, and folic acid) that confer benefits to various subpopulations of women in the United States.

High haemoglobin levels in early pregnancy and gestational diabetes mellitus among Sudanese women

A longitudinal study was carried out to investigate the prevalence and risk factors (including haemoglobin levels) for gestational diabetes mellitus (GDM) in Khartoum, Sudan. The study was carried out at Saad Abuelela Hospital (Khartoum, Sudan) during February to November 2017. Pregnant women in early pregnancy (gestational age <14 weeks) were enrolled in the study. The detailed medical and obstetrics history was recorded for each participant using a questionnaire. The women were then followed up, where a 75-g oral glucose tolerance test was performed at 24 - 28 weeks of gestation. Of 290 women, 259 (89.3%) completed the follow-up. The mean (standard deviation [SD]) of the age, gravidity and gestational age at enrolment were 28.02 (5.7) years, 2.37 (2.42) and 10.86 (2.63) weeks, respectively. Forty-eight women (18.5%) had GDM. Binary regression showed that while age, parity, residence, education and body mass index (BMI) were not associated with GDM, a high haemoglobin level was the only factor associated with GDM (OR = 1.52, 95% confidence interval [CI] = 1.07 - 2.16, p = .019). Women with haemoglobin > 10.8 g/dl were at a higher risk of GDM (OR = 2.52, 95% CI = 1.02 - 6.27, p = .044). There is a high prevalence of GDM, especially among women with high haemoglobin levels.Impact statementWhat is already known on this subject? Gestational diabetes mellitus (GDM) is one of the most common complications during pregnancy, contributing significantly to maternal, perinatal morbidity and mortality and can lead to adverse consequences for the health of both mother and offspring later in life. The rate of GDM varies with the various settings and populations, and a prevalence of 1-14% has been reported depending on the population studied. High haemoglobin levels were recently reported to be associated with GDM.What do the results of this study add? There is a high prevalence of GDM in Khartoum, Sudan, especially among women with high haemoglobin levels in early pregnancy.What are the implications of these findings for clinical practice and/or further research? Haemoglobin levels could be used as reliable markers to detect GDM. These markers could be used in the prevention of GDM.

Association between the ferritin level and risk of gestational diabetes mellitus: A meta-analysis of observational studies

AIMS/INTRODUCTION

The relationship between ferritin and the risk of gestational diabetes mellitus (GDM) has not been established. Thus, we carried out a meta-analysis based on the current literature.

MATERIALS AND METHODS

We searched relevant databases on Embase, PubMed, Cochrane Library and Web of Science before 10 May 2019 to determine the relationship between ferritin and the risk of GDM. The relative risks and 95% confidence intervals of GDM risk were summarized using a random effects model. Studies using categories of ferritin as exposure were combined by dose-response analysis. We carried out both linear and non-linear trends. We also carried out subgroup analysis, whether or not the studies adjusted for potential confounders, and meta-regression analysis to explore the source of heterogeneity. Sensitivity analysis was carried out to explore the robustness of the meta-analysis results.

RESULTS

A total of 10 studies involving 4,690 participants were identified. The summary relative risk comparing persons with the highest concentration categories of ferritin with the lowest concentration categories of ferritin was 1.87 (95% confidence interval 1.50-2.34; I2  = 20.1%). Linear dose-response showed that an increase in ferritin of 10 μg/L increased the risk of GDM by 8% (1.08, 95% confidence interval 1.05-1.13, I2  = 55.1%; n = 4). A non-linear dose-response relationship also showed a consistently increasing risk of GDM with increased ferritin. No evidence of publication bias was detected.

CONCLUSIONS

The findings from this meta-analysis suggest that increased ferritin levels are associated with an increased risk of GDM; however, we require further prospective cohort studies to confirm the results, especially the dose-response relationship between ferritin and GDM.

Effects of prophylactic iron supplementation on outcome of nonanemic pregnant women: A non-randomized clinical trial

BACKGROUND

The aim of the current study was to investigate the effects of prophylactic iron supplementation on the pregnancy outcome of nonanemic pregnant women in a sample of Iranian population.

METHODS

This non-randomized clinical trial was conducted during a 2-year period in obstetrics clinics of Shiraz, southern Iran. We included a sample of singleton pregnancies registered in our clinics. Those with comorbidities were excluded. Serum ferritin was measured at baseline and participants were classified accordingly: those with normal serum ferritin levels (≥30 µg/dL) who received standard prophylactic iron supplementation during the pregnancy (Group 1); those who had minor thalassemia and elevated serum ferritin levels (≥30 µg/dL) who did not receive prophylactic iron supplementation or those with normal ferritin levels (≥30 µg/dL) who refused to receive iron supplementation due to gastrointestinal upset (Group 2); and those with iron deficiency anemia with low serum ferritin levels (<30 µg/dL) who received standard iron supplementation during pregnancy (Group 3). All the participants were followed to the delivery and maternal and neonatal outcomes were recorded and compared between three study groups.

RESULTS

Overall we included 30 pregnant women in each group with mean age of the participants was 28.66 ± 6.02 years. There was no significant difference between three study groups regarding gestational age at delivery (p = 0.250), birthweight (p = 0.893), Apgar at 1 (p = 0.532) and 5 (p = 0.590) minutes, and route of delivery (p = 0.590). The overall rate of maternal complication of the pregnancy was comparable between the three study groups (p = 0.188). However, those in group 1, had significantly higher rate of gestational diabetes mellitus (GDM) when compared to other two groups (p = 0.038).

CONCLUSION

Prophylactic iron supplementation in pregnant women with normal ferritin levels is associated with increased risk of GDM. Other pregnancy and neonatal outcomes are not affected by the prophylactic iron supplementation.

Maternal iron intake during pregnancy and the risk of small for gestational age

Studies of iron and its association with the risk of small for gestational age (SGA) show inconsistent results. Consuming iron supplements during pregnancy is controversial because of possible risks. This study assessed the association between iron intake and the risk of having an SGA newborn and whether iron intake is associated with gestational diabetes. A case-control study of 518 pairs of Spanish women who were pregnant and attending five hospitals was conducted. Groups were matched 1:1 for age (±2 years) and hospital. Cases were women with an SGA newborn at delivery. Controls were women with normal-sized newborns at delivery. Data were gathered on demographic characteristics, socio-economic status, adverse habits (like smoking), and diet. A 137-item food frequency questionnaire was completed. Iron intakes were categorized in quintiles (Q1-Q5). Crude odds ratios (ORs) and adjusted ORs (aORs) with 95% confidence intervals (CIs) were estimated by conditional logistic regression. No significant relationship was found between dietary iron intake and SGA. A protective association was found for women receiving iron supplementation >40 mg/day and SGA versus women not taking supplements (aOR = 0.64, 95% CI [0.42, 0.99]). This association was identified in mothers both with (aOR = 0.57, 95% CI [0.40, 0.81]) and without (aOR = 0.64, 95% CI [0.64, 0.97]) anaemia. In women in the control group without anaemia, iron supplementation >40 mg/day was positively associated with gestational diabetes (aOR = 6.32, 95% CI [1.97, 20.23]). Iron supplementation in pregnancy may prevent SGA independently of existing anaemia but may also increase the risk of gestational diabetes.

Serum Ferritin and Glucose Homeostasis in Women With Recent Gestational Diabetes

OBJECTIVES

Serum markers of iron storage have been linked to type 2 diabetes; however, the mechanism underlying this association is unclear. In pregnancy, increased serum ferritin has been reported in women with gestational diabetes (GDM), a patient population at high risk of future type 2 diabetes. However, in the years after pregnancy, it is not known if ferritin relates to their diabetes risk or the pathophysiologic determinants thereof (insulin sensitivity and beta-cell function). Therefore, we sought to characterize the relationship between ferritin and glucose homeostasis in the early postpartum years in women with and without recent GDM.

METHODS

At both 1 and 3 years postpartum, 340 women (105 with recent GDM) underwent serum ferritin measurement and an oral glucose tolerance test that enabled assessment of insulin sensitivity and/or resistance (Matsuda index and Homeostasis Model Assessment [HOMA-IR]), beta-cell function (Insulin Secretion-Sensitivity Index-2 and insulinogenic index/HOMA-IR) and glucose tolerance.

RESULTS

Serum ferritin did not differ between women who had GDM and their peers at either 1 or 3 years postpartum. Baseline-adjusted change in ferritin between 1 and 3 years correlated with the concomitant change in C-reactive protein (r=0.21, p=0.0002) but was not associated with measures of insulin sensitivity and/or resistance, beta-cell function or glycemia. On adjusted analyses, neither baseline ferritin nor its change from 1 to 3 years was independently associated with any of the following metabolic outcomes at 3-years postpartum: Matsuda index, HOMA-IR, Insulin Secretion-Sensitivity Index-2, insulinogenic index/HOMA-IR, fasting glucose, 2-h glucose or glucose intolerance.

CONCLUSIONS

Serum ferritin is not associated with glucose homeostasis in the early years after a GDM pregnancy.

Association of a plant-based dietary pattern in relation to gestational diabetes mellitus

AIM

The prevalence of gestational diabetes mellitus (GDM), which has adverse effects on mothers and their offspring, is increasing worldwide. The role of a plant-based dietary pattern as a determinant of GDM is not well understood. Therefore, we examined the association between plant-based dietary patterns and the risk of GDM.

METHODS

We enrolled 460 pregnant women in this case-control study, of them 200 were cases and 260 were controls. Dietary intake of participants was evaluated using three 24-hour dietary records. Adherence to the plant-based dietary patterns was scored using three indices of the overall plant-based dietary index (PDI), healthy plant-based diet (hPDI) and unhealthy plant-based diet index (uPDI). The risk of GDM was compared across tertiles of PDI, hPDI and uPDI.

RESULTS

After multivariable adjustment, we demonstrated that the high PDI score was inversely associated with risk of GDM (OR = 0.47; 95% CI: 0.28-0.78, P = 0.004), but there was no significant association between hPDI (OR = 1.03; 95% CI: 0.64-1.65, P = 0.884) or uPDI (OR = 1.65; 95% CI: 0.98-2.78, P = 0.06) and GDM risk.

CONCLUSIONS

We found that following an overall plant-based diet was associated with lower risk of GDM. Future studies are warranted with longitudinal designs to confirm these findings.

The Role of Inflammation in the Development of GDM and the Use of Markers of Inflammation in GDM Screening

Gestational diabetes mellitus is a hyperglycaemic state first recognised in pregnancy. GDM affects both mother and child. Women with GDM and their new-borns are at risk of developing type 2 diabetes in the future. The screening and diagnostic criteria for GDM are inconsistent and thus novel biomarkers of GDM are required to strengthen the screening and diagnostic processes in GDM. Chronic low-grade inflammation is linked to the majority of the well-established risk factors of GDM such as old age, obesity and PCOS. This review provides an overview of the present knowledge on the pathology of GDM, the screening criteria applied, the role of inflammation in the development of GDM and the use of markers of inflammation namely cytokines, oxidative stress markers, lipids, amino acids and iron markers in screening and diagnosis of GDM.

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.

A retrospective study of supplemental iron intake in singleton pregnancy women with risk of developing gestational diabetes mellitus

This study investigated the effect of supplemental iron intake (SII) in early singleton pregnancy women with the risk of developing gestational diabetes mellitus (GDM) among Chinese population.This study included 259 singleton pregnancy participants. Of those, 135 women underwent SII and were assigned to an intervention group, while 124 participants received no SII and were assigned to a control group. The outcome measurements consisted of the number of patients with GDM development, the levels of hemoglobin (Hb) and ferritin, and the outcomes of infant at delivery.No significant difference in the number of patients with GDM development was found between 2 groups at delivery. However, when compared with control group, subjects in the intervention group showed greater efficacy in delivery mode choice of vaginal delivery (P = .04), and cesarean section (P = .01), as well as the birthweight of infants (P < .01). Moreover, Hb and ferritin levels were also significantly higher in the intervention group than those in the control group (P < .01).The results of this retrospective study showed that SII may not increase risk of developing GDM in singleton pregnancy women; and also may benefit both pregnancy women and infants among Chinese population.

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.

Maternal and neonatal outcomes related to iron supplementation or iron status: a summary of meta-analyses

BACKGROUND

Iron deficiency is the most abundant nutritional deficiency in the world and is discussed to be associated with adverse pregnancy outcomes. The objective of this review was to perform an umbrella summary of meta-analyses to evaluate the effects and associations of iron supplementation or iron status on maternal and birth/neonatal outcomes.

METHODS

A literature search was conducted on PubMed and Scopus by two reviewers without temporal restriction. Systematic reviews and meta-analyses of studies evaluating (1) the effects of multimicronutrient compared to iron + folic acid supplementations on maternal and birth/neonatal outcomes (2), the association of dietary iron intake or hemoglobin or ferritin status regarding the risk for maternal (gestational diabetes mellitus (GDM)) and birth/neonatal outcomes, and (3) the effects of iron supplementation on pregnancy and birth/neonatal outcomes, were included in this review.

RESULTS

Overall, 16 meta-analyses were included. Multimicronutrient supplements had significant risk reducing effects on low birth weight and small for gestational age compared to iron/folic acid supplements as controls. Furthermore, most of the meta-analyses showed that higher levels of hemoglobin or ferritin increased the risk for GDM. On the other hand, maternal anemia (low hemoglobin levels) was associated with adverse birth/neonatal outcomes. Finally, iron supplementation reduced the risk of iron deficiency and iron deficiency anemia and had some risk reducing effects on low birth weight newborns.

CONCLUSIONS

Our summary of meta-analyses showed that multimicronutrient supplementation had beneficial effects on some neonatal outcomes. Furthermore, higher ferritin levels seem to increase the risk for GDM whereas maternal anemia was associated with adverse birth/neonatal outcomes.

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.

The Role of Iron in Type 1 Diabetes Etiology: A Systematic Review of New Evidence on a Long-Standing Mystery

BACKGROUND

The incidence of type 1 diabetes (T1D) is rising, which might be due to the influence of environmental factors. Biological and epidemiological evidence has shown that excess iron is associated with beta-cell damage and impaired insulin secretion.

AIM

In this review, our aim was to assess the association between iron and the risk of T1D.

METHODS

A systematic literature search was performed in PubMed and EMBASE in July 2016. Studies investigating the effect of iron status/intake on the risk of developing T1D later were included, and study quality was evaluated. The results have been summarized in narrative form.

RESULTS

From a total of 931 studies screened, we included 4 observational studies evaluating iron intake from drinking water or food during early life and the risk of T1D. The quality of the studies was moderate to high assessed via the nine-star Newcastle Ottawa Scale. One out of the four studies included in this review found estimates of dietary iron intake to be associated with risk of T1D development, whereas three studies found no such relationship for estimates of iron in drinking water.

CONCLUSIONS

The limited number of studies included found dietary iron, but not iron in drinking water, to be associated with risk of T1D. Further studies are needed to clarify the association between iron and risk of T1D, especially studies including measurements of body iron status.

Maternal iron intake during pregnancy and birth outcomes: a cross-sectional study in Northwest China

Previous studies have yielded conflicting results on the associations of maternal Fe intake with birth outcomes. This study aimed to investigate the associations between maternal Fe intake (total Fe from diet and supplements, dietary total Fe, haeme Fe, non-haeme Fe and Fe supplements use) and adverse birth outcomes in Shaanxi Province of Northwest China. In all, 7375 women were recruited using a stratified multistage random sampling method at 0-12 months (median 3; 10th-90th percentile 0-7) after delivery. Diets were collected by a validated FFQ and maternal characteristics were obtained via a standard questionnaire. The highest tertile of haeme Fe intake compared with the lowest tertile was negatively associated with low birth weight (LBW) (OR 0·68; 95 % CI 0·49, 0·94), small for gestational age (SGA) (OR 0·76; 95 % CI 0·62, 0·94) and birth defects (OR 0·55; 95 % CI 0·32, 0·89). Maternal haeme Fe intake was associated with a lower risk of intra-uterine growth retardation (IUGR) (medium tertile v. lowest tertile: OR 0·78; 95 % CI 0·61, 0·95; highest tertile v. lowest tertile: OR 0·76; 95 % CI 0·59, 0·93; P trend=0·045). The OR of LBW associated with Fe supplements use were as follows: during pregnancy: 0·72 (95 % CI 0·50, 0·95); in the second trimester: 0·67 (95 % CI 0·42, 0·98); in the third trimester: 0·47 (95 % CI 0·24, 0·93). We observed no associations of total Fe, dietary total Fe or non-haeme Fe intake with birth outcomes. The results suggest that maternal haeme Fe intake is associated with a reduced risk of LBW, SGA, IUGR and birth defects, and Fe supplements use during pregnancy reduces LBW risk.

Associations of polymorphisms in the candidate genes for Alzheimer's disease BIN1, CLU, CR1 and PICALM with gestational diabetes and impaired glucose tolerance

Alzheimer's disease (AD) is the most common type of dementia, with a prevalence that is rising every year. AD is associated with type 2 diabetes mellitus (T2DM) and insulin resistance, and is therefore sometimes called "type 3 diabetes mellitus". The aim of this study was to examine whether the variants of some candidate genes involved in the development of AD, namely BIN1 (rs744373), CLU (rs11136000), CR1 (rs3818361), and PICALM (rs3851179), are related to several disorders of glucose metabolism-gestational diabetes (GDM), T2DM and impaired glucose tolerance (IGT). Our study included 550 women with former GDM and 717 control women, 392 patients with T2DM and 180 non-diabetic controls, and 117 patients with IGT and 630 controls with normal glucose tolerance. Genotyping analysis was performed using specially-designed TaqMan assays. No significant associations of the genetic variants rs744373 in BIN1, rs11136000 in CLU, or rs3818361 in CR1 were found with GDM, T2DM or IGT, but rs3851179 in PICALM was associated with an increased risk of GDM. The frequency of the AD risk-associated C allele was significantly higher in the GDM group compared to controls: OR 1.21; 95% CI (1.03-1.44). This finding was not apparent in T2DM and IGT; conversely, the C allele of the PICALM SNP was protective for IGT: OR 0.67; 95% CI (0.51-0.89). This study demonstrates an association between PICALM rs3851179 and GDM as well as IGT. However, elucidation of the possible role of this gene in the pathogenesis of GDM requires further independent studies.

Haemoconcentration risk at the end of pregnancy: effects on neonatal behaviour

OBJECTIVE

To determine the associations between haemoconcentration at the end of pregnancy (third trimester and delivery) and neonatal behaviour in healthy pregnant women supplemented with moderate doses of Fe.

DESIGN

A prospective longitudinal study in which obstetric and clinical history, maternal toxic habits, maternal anxiety and Hb levels were recorded at the third trimester and delivery. Neonatal behaviour was assessed at 48-72 h of age using the Neonatal Behavioral Assessment Scale.

SETTING

Unit of Obstetrics and Gynaecology of the Sant Joan University Hospital in Reus, Tarragona (Spain).

SUBJECTS

A total of 210 healthy and well-nourished pregnant women and their full-term, normal-weight newborns.

RESULTS

The results showed that, after adjusting for confounders, in the third trimester the risk of haemoconcentration (6·2 % of pregnant women) was related to decreased neonatal state regulation (B=-1·273, P=0·006) and alertness (B=-1·848, P=0·006) scores. In addition, the risk of haemoconcentration at delivery (12·0 % of pregnant women) was also related to decreased neonatal state regulation (B=-0·796, P=0·021) and poor robustness and endurance (B=-0·921, P=0·005) scores.

CONCLUSIONS

Our results show that the risk of haemoconcentration at the end of pregnancy is related to the neonate's neurodevelopment (and self-regulation capabilities), suggesting that Fe supplementation patterns and maternal Fe status during pregnancy are important factors for neurodevelopment which may be carefully controlled.

A longitudinal study of iron status during pregnancy and the risk of gestational diabetes: findings from a prospective, multiracial cohort

AIMS/HYPOTHESIS

The aim of this study was to prospectively and longitudinally investigate maternal iron status during early to mid-pregnancy, and subsequent risk of gestational diabetes mellitus (GDM), using a comprehensive panel of conventional and novel iron biomarkers.

METHODS

A case-control study of 107 women with GDM and 214 controls (matched on age, race/ethnicity and gestational week during blood collection) was conducted within the the Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies-Singleton Cohort (2009-2013), a prospective and multiracial pregnancy cohort. Plasma hepcidin, ferritin and soluble transferrin receptor (sTfR) were measured and sTfR:ferritin ratio was derived, twice before GDM diagnosis (gestational weeks 10-14 and 15-26) and at weeks 23-31 and 33-39. GDM diagnosis was ascertained from medical records. Adjusted ORs (aORs) for GDM were estimated using conditional logistic regression analysis, adjusting for demographics, prepregnancy BMI and other major risk factors.

RESULTS

Hepcidin concentrations during weeks 15-26 were 16% higher among women with GDM vs controls (median 6.4 vs 5.5 ng/ml; p = 0.02 ), and were positively associated with GDM risk; the aOR (95% CI) for highest vs lowest quartile was 2.61 (1.07, 6.36). Ferritin levels were also positively associated with GDM risk; the aOR (95% CI) for highest vs lowest quartile was 2.43 (1.12, 5.28) at weeks 10-14 and 3.95 (1.38, 11.30) at weeks 15-26. The sTfR:ferritin ratio was inversely related to GDM risk; the aOR (95% CI) for highest vs lowest quartile was 0.33 (0.14, 0.80) at weeks 10-14 and 0.15 (0.05, 0.48) at weeks 15-26.

CONCLUSIONS/INTERPRETATION

Our findings suggest that elevated iron stores may be involved in the development of GDM from as early as the first trimester. This raises potential concerns for the recommendation of routine iron supplementation among iron-replete pregnant women.

Iron: how much is too much?

Gross iron overload has long been known to result in diabetes mellitus. However, it is now thought that milder levels of iron overload, possibly within the normal range, also increase the risk of diabetes mellitus. The article by Rawal et al in this issue (Diabetologia doi: 10.1007/s00125-016-4149-3 ) provides further support for the relationship between mild degrees of iron overload and the risk of gestational diabetes. The purpose of this commentary is to briefly discuss the background of this relationship and the implications it may have for routine pregnancy care.

Early Pregnancy Biochemical Predictors of Gestational Diabetes Mellitus

PURPOSE OF REVIEW

Universal oral glucose tolerance-based screening is employed to identify pregnant women with gestational diabetes mellitus (GDM), as treatment of this condition decreases the risk of associated complications. A simple and accurate blood test which identifies women at low or high risk for GDM in the first trimester would have the potential to decrease costs and improve outcomes through prevention or treatment. This review summarizes published data on early pregnancy biomarkers which have been tested as predictors of GDM.

RECENT FINDINGS

A large number of first-trimester biochemical predictors of GDM have been reported, mostly in small case-control studies. These include glycemic markers (fasting glucose, post-load glucose, hemoglobin A1C), inflammatory markers (C-reactive protein, tumor necrosis factor-alpha), insulin resistance markers (fasting insulin, sex hormone-binding globulin), adipocyte-derived markers (adiponectin, leptin), placenta-derived markers (follistatin-like-3, placental growth factor, placental exosomes), and others (e.g., glycosylated fibronectin, soluble (pro)renin receptor, alanine aminotransferase, ferritin). A few large studies suggest that first-trimester fasting glucose or hemoglobin A1C may be useful for identifying women who would benefit from early GDM treatment. To translate the findings from observational studies of first-trimester biomarkers for GDM to clinical practice, trials or cost-effectiveness analyses of screening and treatment strategies based on these novel biomarkers are needed.

Elevated iron status and risk of gestational diabetes mellitus: A systematic review and meta-analysis

The aim of this systematic review and meta-analysis of observational studies was to assess the relationship between elevated iron status, measured as hemoglobin and ferritin levels, and the risk of gestational diabetes mellitus (GDM). The present study was recorded in PROSPERO (2013:CRD42013005717). The selected studies were identified through a systematic review of scientific literature published in The Cochrane Library and PubMed/MEDLINE databases from their inception until March 10, 2016, in addition to citation tracking and hand-searches. The search strategy of original articles combined several terms for hemoglobin, ferritin, pregnancy, and GDM. OR and 95% CI of the selected studies were used to identify associations between hemoglobin and/or ferritin levels with the risk of GDM. Summary estimates were calculated by combining inverse-variance using fixed-effects model. 2468 abstracts were initially found during the search. Of these, 11 with hemoglobin and/or ferritin data were selected for the meta-analyses. We observed that high hemoglobin (OR = 1.52; 95% CI: 1.23-1.88), as well as ferritin (OR = 2.09; 95% CI: 1.48-2.96) levels were linked to an increased risk of GDM. Low heterogeneity was observed in hemoglobin (I²  = 33.3%, P = 0.151) and ferritin (I²  = 0.7%, P = 0.418) meta-analyses, respectively. Publication bias was not appreciated. High hemoglobin or ferritin levels increase the risk of GDM by more than 50% and more than double, respectively, in the first and third trimester. Therefore, determining of hemoglobin or ferritin concentration in early pregnancy might be a useful tool for recognizing pregnant women at risk of GDM.

Prediction and prevention of Gestational Diabetes: an update of recent literature

A diagnosis of Gestational Diabetes (GDM) confers adverse risk to the health of the mother and fetus both in pregnancy and later life. The background rate in pregnancy varies between 2 and 14% with incidences reported to be as high as 40% in obese populations. GDM diagnoses are escalating because of rising numbers of overweight and obesity in the reproductive age group but also because of different screening and diagnostic criteria. Lifestyle modification in those diagnosed with GDM has been proven to be an effective treatment in attenuating the metabolic dysregulation associated with this and potentially avoiding the need for medical therapy with either metformin or insulin. Emerging evidence in previous years suggests lifestyle interventions (dietary±physical activity and behavior modification) either pre-pregnancy or antenatally may reduce the incidence of GDM. The first trimester is also becoming an important interrogation period for the prediction of many adverse obstetric outcomes including abnormal glucose metabolism. This review outlines the most contemporary evidence on the prediction and non-pharmacological antenatal prevention strategies used for Gestational Diabetes.