Does high maternal first trimester iron status have an effect on the 50 g oral glucose test?

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.

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.

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.

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.

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

AIM

High iron measured using dietary intake and biomarkers is associated with Type 2 diabetes. It is uncertain whether a similar association exists for gestational diabetes mellitus. The aim of this systematic review was to conduct a cohort study examining first trimester body iron stores and subsequent risk of gestational diabetes, and to include these findings in a systematic review of all studies examining the association between maternal iron status, iron intake (dietary and supplemental) and the risk of gestational diabetes.

METHODS

Serum samples from women with first trimester screening were linked to birth and hospital records for data on maternal characteristics and gestational diabetes diagnosis. Blood was analysed for ferritin, soluble transferrin receptor and C-reactive protein. Associations between iron biomarkers and gestational diabetes were assessed using multivariate logistic regression. A systematic review and meta-analysis, registered with PROSPERO (CRD42014013663) included studies of all designs published in English from January 1995 to July 2015 that examined the association between iron and gestational diabetes and included an appropriate comparison group.

RESULTS

Of 3776 women, 3.4% subsequently developed gestational diabetes. Adjusted analyses found increased odds of gestational diabetes for ferritin (OR 1.41; 95% CI 1.11, 1.78), but not for soluble transferrin receptor (OR 1.00; 95% CI 0.97, 1.03) per unit increase of the biomarker. Two trials of iron supplementation found no association with gestational diabetes. Increased risk of gestational diabetes was associated with higher levels of ferritin and serum iron and dietary haem iron intakes.

CONCLUSIONS

Increased risk of gestational diabetes among women with high serum ferritin and iron levels and dietary haem iron intakes warrants further investigation.

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.