Association of maternal folate status in the second trimester of pregnancy with the risk of gestational diabetes mellitus

The Significance of Genetically Determined Methylation and Folate Metabolism Disorders in the Pathogenesis of Coronary Artery Disease: A Target for New Therapies?

Methylation is a biochemical process involving the addition of a methyl group (-CH3) to various chemical compounds. It plays a crucial role in maintaining the homeostasis of the endothelium, which lines the interior surface of blood vessels, and has been linked, among other conditions, to coronary artery disease (CAD). Despite significant progress in CAD diagnosis and treatment, intensive research continues into genotypic and phenotypic CAD biomarkers. This review explores the significance of the methylation pathway and folate metabolism in CAD pathogenesis, with a focus on endothelial dysfunction resulting from deficiency in the active form of folate (5-MTHF). We discuss emerging areas of research into CAD biomarkers and factors influencing the methylation process. By highlighting genetically determined methylation disorders, particularly the MTHFR polymorphism, we propose the potential use of the active form of folate (5-MTHF) as a novel CAD biomarker and personalized pharmaceutical for selected patient groups. Our aim is to improve the identification of individuals at high risk of CAD and enhance their prognosis.

Folate supplementation as a beneficial add-on treatment in relieving depressive symptoms: A meta-analysis of meta-analyses

The results of meta-analyses investigating the role of folate on depression are conflicting. The aim of this umbrella meta-analysis was to obtain an overall effect and give a concise and resolving conclusion. International scientific databases including PubMed, Scopus, and Web of Science were searched up to Oct 2023. All observational and interventional meta-analyses investigating the role of folate in depression were included in the study. Random-effects model was employed to obtain pooled results. I 2 statistics and Cochrane Q test were used to assess the between-study heterogeneity. The quality of included meta-analyses was evaluated using the Assessing the Methodological Quality of Systematic Reviews 2 (AMSTAR2) questionnaire. Overall 11 studies were included, of which 8 studies went under quantitative evaluation. The results indicated that folate supplementation significantly relieved depression symptoms [(SMD: -0.42; 95% CI: -0.57, -0.27, p < .001; I 2 = 0.0%, p-heterogeneity = 0.554) (WMD: -3.20; 95% CI: -4.00, -2.41, p < .001, I 2 = 14.8%, p-heterogeneity = 0.318)] with low levels of heterogeneity. Also, based on observational studies, folate insufficiency significantly increased the odds ratio of depression by 35% (OR:1.35; 95% CI: 1.27, 1.42, p < .001, I 2 = 8.7%, p-heterogeneity = 0.350). The findings support the fact that folate supplementation could be suggested as an efficacious and adjuvant agent in the alleviation of depression symptoms along with routine medications.

Gestational diabetes mellitus is associated with distinct folate-related metabolites in early and mid-pregnancy: A prospective cohort study

AIMS

This study aimed to evaluate the association between gestational diabetes mellitus (GDM) and circulating folate metabolites, folic acid (FA) intake, and the methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) genotype.

MATERIALS AND METHODS

A prospective pregnancy cohort study was conducted in Beijing, China, from 2022 to 2023. Circulating folate metabolites, including red blood cell (RBC) 5-methyltetrahydrofolate (5-MTHF), 5, 10-methylene-tetrahydrofolate (5,10-CH2-THF), 5- formyltetrahydrofolate (5-CHO-THF), and unmetabolised folic acid (UMFA), and plasma homocysteine (HCY), 5-MTHF, and methylmalonic acid (MMA), were determined at 6-17 weeks and 20-26 weeks of gestation. FA intake and the MTHFR and MTRR genotype were also examined. GDM was diagnosed between 24 and 28 weeks of pregnancy by a 75-g oral glucose tolerance test (OGTT). The association between the folate status and GDM was ascertained using multivariate generalised linear models, logistic regression models, and restricted cubic spline regression, adjusting for potential confounders.

RESULTS

The study included 2032 pregnant women, of whom 392 (19.29%) developed GDM. UMFA above the 75th percentile (≥P75) [adjusted OR (aOR) (95% confidence interval [CI]) = 1.36 (1.01-1.84)], UMFA ≥ P90 [aOR (95% CI) = 1.82 (1.23-2.69)], and HCY ≥ P75 [aOR (95% CI) = 1.40 (1.04-1.88)] in early pregnancy, and RBC 5-MTHF [aOR (95% CI) = 1.48 (1.10-2.00)], RBC 5,10-CH2-THF [aOR (95% CI) = 1.55 (1.15-2.10)], and plasma 5-MTHF [aOR (95% CI) = 1.36 (1.00-1.86)] in mid-pregnancy ≥ P75 are associated with GDM. Higher UMFA levels in early pregnancy show positive associations with the 1-h and 2-h glucose levels during the OGTT, and higher HCY levels are associated with increased fasting glucose levels during the OGTT. In comparison, RBC 5- MTHF and 5,10-CH2-THF, and plasma 5- MTHF in mid-pregnancy are positively associated with the 1-h glucose level (p < 0.05). The MTHFR and MTRR genotype and FA intake are not associated with GDM.

CONCLUSIONS

Elevated levels of UMFA and HCY during early pregnancy, along with elevated RBC 5-MTHF and 5,10-CH2-THF and plasma 5-MTHF during mid-pregnancy, are associated with GDM. These findings indicate distinct connections between different folate metabolites and the occurrence of GDM.

Risk Factors for Hypoglycemia Among Neonates: A Prospective Cohort Study Among Pregnant People With Gestational Diabetes Mellitus

OBJECTIVE

Neonatal hypoglycemia (NH) is the most frequent complication in neonates born to pregnant people with gestational diabetes mellitus (GDM) and an important cause of brain damage and death of neonates. We explored the risk factors for NH in neonates of pregnant people with GDM.

METHODS

A prospective cohort study was conducted involving 322 pregnant people with GDM at the Guangzhou Women and Children's Medical Centre. Maternal sociodemographic, clinical, and biochemical data, as well as general characteristics of neonates, were collected to analyze their associations with NH in neonates of pregnant people with GDM.

RESULTS

The incidence of NH among neonates of pregnant people with GDM was 19.57% (63/322). After adjustment for confounders, the factors significantly associated with an increased risk of NH were cesarean delivery (relative risk [RR] = 3.44; 95% confidence interval [CI], 1.83-6.45), red blood cell (RBC) count (RR = 2.19; 95% CI, 1.22-3.96), and 1-hour postprandial glucose (RR = 2.35; 95% CI, 1.23-4.46) during pregnancy, whereas later gestational age (RR = 0.58; 95% CI, 0.42-0.80) and multiparity (RR = 0.32; 95% CI, 0.16-0.66) were associated with a reduced risk of NH.

CONCLUSION

Cesarean delivery, maternal 1-hour glucose of the oral glucose tolerance test, and increased RBC count of pregnant people with GDM are independent risk factors for NH, while later gestational age and multiparity are protective factors.

Uncovering the Hidden Dangers and Molecular Mechanisms of Excess Folate: A Narrative Review

This review delves into the intricate relationship between excess folate (vitamin B9) intake, especially its synthetic form, namely, folic acid, and its implications on health and disease. While folate plays a pivotal role in the one-carbon cycle, which is essential for DNA synthesis, repair, and methylation, concerns arise about its excessive intake. The literature underscores potential deleterious effects, such as an increased risk of carcinogenesis; disruption in DNA methylation; and impacts on embryogenesis, pregnancy outcomes, neurodevelopment, and disease risk. Notably, these consequences stretch beyond the immediate effects, potentially influencing future generations through epigenetic reprogramming. The molecular mechanisms underlying these effects were examined, including altered one-carbon metabolism, the accumulation of unmetabolized folic acid, vitamin-B12-dependent mechanisms, altered methylation patterns, and interactions with critical receptors and signaling pathways. Furthermore, differences in the effects and mechanisms mediated by folic acid compared with natural folate are highlighted. Given the widespread folic acid supplementation, it is imperative to further research its optimal intake levels and the molecular pathways impacted by its excessive intake, ensuring the health and well-being of the global population.

Diverse associations observed between pregnancy complications and RBC or plasma folates determined by an in-house developed LC-MS/MS method

BACKGROUND

As folates are essential for embryonic development and growth, it is necessary to accurately determine the levels of folates in plasma and red blood cells (RBCs) for clinical intervention. The aims of this study were to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantitation of folates in plasma and RBCs and to examine the association between plasma and RBC folate concentrations and gestational diabetes mellitus (GDM), gestational hypertension (GH) and preeclampsia (PE).

METHODS

With the in-house developed LC-MS/MS, a retrospective cross-sectional study was conducted. The healthy pregnant women of first- (n = 147), second- (n = 84) and third-trimester (n = 141) or the women diagnosed with GDM (n = 84), GH (n = 58) or PE (n = 23), that were aged between 22 and 46 years old and registered at our institute, were subjected for measurement of folic acid (FA) and 5-methyltetrahydrofolate (5-MTHF), followed by appropriate statistical association analysis.

RESULTS

The assay for simultaneous quantitation of FA and 5-MTHF in plasma and RBCs was linear, stable, with imprecision less than 15% and recoveries within ±10%. The lower limits of quantification for FA and 5-MTHF measurement in whole blood were 0.57 and 1.09 nmol/L, and in plasma were 0.5 and 1 nmol/L, respectively. In the association analysis, the patients with lower RBC folate level (<906 nmol/L) presented higher risks of PE development (OR 4.861 [95% CI 1.411-16.505]) by logistic regression and restricted cubic spline (RCS) regression in a nonlinear fashion. In addition, higher level of plasma folates in pregnancy was significantly associated with GH risk but may be protective for the development of GDM.

CONCLUSIONS

The in-house developed LC-MS/MS method for folates and metabolites in plasma or RBC showed satisfactory analytical performance for clinical application. Further, the levels of folates and metabolites were diversely associated with GDM, GH and PE development.

The Influence of Maternal Folate Status on Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis

Maternal folate has been shown to relate to the risk of gestational diabetes mellitus (GDM). However, the existing studies have yielded inconsistent conclusions. The purpose of this study was to systematically review the association between maternal folate status and the risk of GDM. Observational studies up to 31 October 2022 were included. Study characteristics, the means and standard deviations (SDs) of folate levels (serum/red blood cell (RBC)), the odds ratios (ORs) with 95% confidence intervals (CIs) and the time for folate measurement were extracted. Compared with the non-GDM group, serum and RBC folate levels in women with GDM were significantly higher. Our subgroup analysis demonstrated that serum folate levels in the GDM group were significantly higher than in the non-GDM group only in the second trimester. RBC folate levels in the GDM group were significantly higher than in the non-GDM group in the first and second trimesters. Taking serum/RBC folate levels as continuous variables, the adjusted odds ratios of GDM risk showed that increased serum folate concentration rather than RBC folate elevated the risk of GDM. In the descriptive analysis, five studies reported high serum folate levels increased GDM risk, whereas the other five showed no association between serum folate levels and GDM risk. Moreover, the rest three studies pointed out high RBC folate levels increased GDM risk. Altogether we found that the risk of GDM is associated with high serum/plasma and RBC folate levels. Future studies should determine the recommended folic acid cutoff balancing the risk for GDM and fetal malformations.

Is the Tradeoff between Folic Acid or/and Multivitamin Supplementation against Birth Defects in Early Pregnancy Reconsidered? Evidence Based on a Chinese Birth Cohort Study

BACKGROUND

Several studies have reported conflicting results on the association between maternal exposure to folic acid (FA) and/or multivitamin (MV) supplements and the risk of birth defects (BDs), especially for different subtypes of BDs. The present study aimed to identify the association between maternal exposure to FA or/and MV and BDs in offspring.

METHODS

In the Chinese Birth Cohort Study initiated from 20 November 2017, 120,652 pregnant women completed follow-up until 20 August 2021. The participants were classified into four groups: without exposure to FA and MV, exposure to only FA, exposure to only MV, and exposure to FA and MV. Birth defects were coded by the International Classification of Diseases (ICD)-10. In order to explore the structural relationship between maternal FA or MV supplements and BDs, directed acyclic graphs were drawn. Then, an inverse probability treatment weighting was utilized to reduce the systematic differences in the baseline characteristics among the different groups. Lastly, a two-level mixed-effect log binomial regression analysis was used to estimate the relative risk (RR) value of the different subtypes of BDs under different exposures to FA and/or MV.

RESULTS

Compared with the maternal group without exposure to FA and MV, the RR values of nervous system defects, face, ear, and neck defects, limb defects, and CHDs in the maternal group with only FA supplementation were less than 1.0, but they were not statistically significant. The RR values of genitourinary defects, abnormal chromosomes, and oral clefts were more than 1.0, and they were also not statistically significant. However, the risk of genitourinary defects (RR: 3.22, 95% CI: 1.42-7.29) and chromosomal abnormalities (RR: 2.57, 95% CI: 1.16-5.73) in the maternal group with only MV supplementation increased more than those in the maternal group without exposure to FA and MV. In addition, the RR values of all subtypes of BDs in the maternal group with exposure to FA and MV were closer to 1.0 than those in maternal group with exposure to only MV, but they were not statistically significant.

CONCLUSIONS

It was indicated that the simultaneous supplementation of FA and MV in early pregnancy may have an interaction for the prevention of BDs and may have inconsistent effects for different subtypes of BDs. At the same time, excessive FA supplementation in pregnant women may increase the risk of BDs in their offspring. Although the mechanism is not clear, this evidence reminded us that more trade-offs are necessary for formulating strategies for the prevention of BDs with FA and/or MV supplementation in early pregnancy.

High Folate, Perturbed One-Carbon Metabolism and Gestational Diabetes Mellitus

Folate is a dietary micronutrient essential to one-carbon metabolism. The World Health Organisation recommends folic acid (FA) supplementation pre-conception and in early pregnancy to reduce the risk of fetal neural tube defects (NTDs). Subsequently, many countries (~92) have mandatory FA fortification policies, as well as recommendations for periconceptional FA supplementation. Mandatory fortification initiatives have been largely successful in reducing the incidence of NTDs. However, humans have limited capacity to incorporate FA into the one-carbon metabolic pathway, resulting in the increasingly ubiquitous presence of circulating unmetabolised folic acid (uFA). Excess FA intake has emerged as a risk factor in gestational diabetes mellitus (GDM). Several other one-carbon metabolism components (vitamin B12, homocysteine and choline-derived betaine) are also closely entwined with GDM risk, suggesting a role for one-carbon metabolism in GDM pathogenesis. There is growing evidence from in vitro and animal studies suggesting a role for excess FA in dysregulation of one-carbon metabolism. Specifically, high levels of FA reduce methylenetetrahydrofolate reductase (MTHFR) activity, dysregulate the balance of thymidylate synthase (TS) and methionine synthase (MTR) activity, and elevate homocysteine. High homocysteine is associated with increased oxidative stress and trophoblast apoptosis and reduced human chorionic gonadotrophin (hCG) secretion and pancreatic β-cell function. While the relationship between high FA, perturbed one-carbon metabolism and GDM pathogenesis is not yet fully understood, here we summarise the current state of knowledge. Given rising rates of GDM, now estimated to be 14% globally, and widespread FA food fortification, further research is urgently needed to elucidate the mechanisms which underpin GDM pathogenesis.

Micronutrients of the one-carbon metabolism cycle are altered in mothers and neonates by gestational diabetes and are associated with weight, height and head circumference at birth

While several studies have previously described the levels of one-carbon metabolism-related micronutrients in women with gestational diabetes mellitus (GDM) and their neonates, the results in these literature reports have been contradictory. We hypothesized that the concentrations of micronutrients involved in the one-carbon cycle are altered in pregnant women and their neonates by GDM, and that these changes could further modify the neonatal anthropometry. Micronutrient levels were measured in 123 pregnant women with normal glucose levels (M-ND) and their neonates (N-ND), as well as in 54 pregnant women with gestational diabetes (M-GDM) and their neonates (M-GDM). Folate and vitamin B12 levels were measured via competitive ELISA, and betaine, choline, and glycine levels were measured via ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS/MS). Vitamin B12 and Glycine were found to be higher in M-GDM compared to M-ND. N-GDM had higher levels of folic acid and vitamin B12 and lower levels of betaine and choline compared to N-ND. In general, neonates presented with high concentrations of micronutrients compared to their mothers, and the fetus/maternal ratio of micronutrients was higher among the N-ND as compared to the N-GDM. Micronutrients were also variably associated with anthropometric measurements. The association of betaine with neonatal anthropometry in N-GDM is highlighted. In summary, our results implicate a potential role of GDM in altering the levels of one-carbon metabolism-related micronutrients among pregnant women and their neonates. Likewise, our results also elucidate a potential association between the concentrations of micronutrients and the weight, height, and head circumference of neonates.

Associations of Maternal rs1801131 Genotype in MTHFR and Serum Folate and Vitamin B12 with Gestational Diabetes Mellitus in Chinese Pregnant Women

Circumstantial evidence links one-carbon metabolism (OCM) related nutrients, such as folate and vitamin B₁₂, with gestational diabetes mellitus (GDM). However, few studies have evaluated the combined effects of these nutrients with OCM related gene polymorphisms on GDM. This study investigated whether OCM related genetic variants modified the associations of folate and B₁₂ with GDM. Logistic regression was used to estimate odds ratios (ORs) for OCM related nutrients and single nucleotide polymorphisms (SNPs) in genes encoding main OCM related enzymes (MTHFR, MTR, and MTRR) on GDM. Higher folate concentrations were associated with increased GDM risk (OR: 1.59; 95% CI: 1.22, 2.13). However, higher B₁₂ concentrations were associated with reduced GDM risk (OR: 0.76; 95% CI: 0.65, 0.92). Pregnancies with MTHFR rs1801131 G alleles had a significantly lower risk of GDM than pregnancies with T alleles (OR: 0.65; 95% CI: 0.47, 0.91) under the dominant model. The genotype-stratified analysis revealed the association between folate and GDM (OR: 1.66, 95% CI: 1.20, 2.30) or B₁₂ and GDM (OR: 0.80, 95% CI: 0.65, 0.98) was more evident in pregnancies with TT genotype. Higher folate and lower B₁₂ are associated with GDM. Pregnancies with MTHFR rs1801131 TT genotype are more susceptible to OCM nutrient-related GDM.

Effects of maternal folate and vitamin B12 on gestational diabetes mellitus: a dose-response meta-analysis of observational studies

To comprehensively estimate the association of gestational diabetes mellitus (GDM) risk with maternal red blood cell (RBC) folate, plasma/serum folate, dose and duration of folic acid supplement (FAS) intake and vitamin B12 separately. PubMed, Web of science, CNKI, and Wanfang Databases were searched through March 26, 2021. We synthesized data using random-effects model meta-analysis in Stata 12.0. Sensitivity, subgroup and dose-response analyses were also performed. The certainty of evidence was evaluated using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE). Twenty six datasets from thirteen eligible observational studies were included in the study. We found a significant increase of GDM risk with the highest versus lowest category of RBC folate (OR = 1.96, 95% CI: 1.48-2.61, I2 = 0.0%, moderate-certainty evidence) and plasma/serum folate (OR = 1.23, 1.02-1.48, I2 = 57.8%, low-certainty evidence). The dose-response analysis revealed that each 200 ng/ml increase in RBC folate was significantly associated with 8% higher GDM risk. No significant association between dose of FAS intake and GDM risk was found with very low cetainty. Meanwhile, longer duration (≥3 months) of FAS conferred 56% significant higher GDM risk (OR = 1.56, 1.02-2.39, very low certainty evidence). No significant association of GDM risk with highest plasma/serum B12 was observed compared to lowest B12 (OR = 0.77, 0.58-1.02, very low-certainty evidence). Moderate-certainty evidence suggests that higher RBC folate appears to significantly increase GDM risk. Higher plasma/serum folate may increase GDM risk but with low certainty. Further well-designed trials or prospective studies are needed.

The Effects of Serum Folic Acid and Vitamin B12 on the Risk of Gestational Diabetes Mellitus

PURPOSE

In order to gain more knowledge on the risk of gestational diabetes mellitus (GDM), and to provide evidence for clinical guidance on the optimum level of serum folic acid and vitamin B12, this study aimed to clarify the relationship between serum folic acid and vitamin B12 and the risk of GDM.

PATIENTS AND METHODS

This retrospective case-control study was conducted based on the clinical information system of the Maternal and Child Health Hospital of Hubei Province. Clinical data including maternal socio-demographical characteristics, serum folic acid, and vitamin B12 were collected. Logistic regression analyses and restricted cubic splines were performed to examine the impact of serum folic acid and vitamin B12 on the risk of GDM.

RESULTS

Significantly elevated risks of GDM were observed in groups with high serum folic acid concentration (OR = 1.84, 95% CI: 1.07-3.16), and in low vitamin B12 concentration (OR = 2.14, 95% CI: 1.26-3.65). After stratified by age, the increased risk of GDM was still noticed in a low level of vitamin B12 among mothers aged <30 years (OR = 4.76, 95% CI: 1.45-15.61). In mothers with pre-pregnancy BMI <24, elevated risk of GDM was significantly associated with a high folic acid (OR = 2.09, 95% CI: 1.11-3.93) or a low vitamin B12 concentration (OR = 2.24, 95% CI: 1.22-4.14). Moreover, the risk of GDM was on the decline with the increased level of folic acid in the beginning, and it started to manifest an upward trend when the serum folic acid reached 19.02 ng/mL.

CONCLUSION

This study demonstrated that serum folic acid excess or vitamin B12 deficiency could contribute to the increased risk of GDM, and revealed the potential side effect of serum folic acid overdose. As serum folic acid and vitamin B12 tests are widely applied in clinical practice, this finding could help clinicians to evaluate maternal risk from a new perspective.

Imbalanced Folate and Vitamin B12 in the Third Trimester of Pregnancy and its Association with Birthweight and Child Growth up to 2 Years

SCOPE

Folic acid supplementation during pregnancy may lead to an imbalance when vitamin B12 intake is low (folate trap) and may affect child's growth.

METHODS

The authors study the association between third trimester maternal intakes of folate and B12 and birthweight and postnatal growth of 2632 infants from the KOALA Birth Cohort Study. Plasma vitamin biomarkers are measured in 1219 women.

RESULTS

Imbalanced total intakes (folate > 430 µg day^-1 combined with B12 < 5.5 µg day^-1 ) are not associated with birthweight [β adj (95% CI) = -14.87 (-68.87, 39.13)] compared with high intakes of both. Imbalanced intake is associated with a lower z score of weight at 1-2 years [β adj = -0.14 (-0.25, -0.03)]. Having red blood cell folate > 745 nmol L^-1 and plasma B12 < 172 pmol L^-1 is not associated with birthweight [β adj = -7.10 (-97.90, 83.71) g]. Maternal dietary B12 intake [β adj = -9.5 (-15.6, -3.3)] and plasma methylmalonic acid [β adj = 234 (43, 426)] are associated with birthweight.

CONCLUSION

Low maternal dietary B12 intake and elevated methylmalonic acid rather than imbalanced vitamins are associated with higher birthweight, suggesting that low maternal B12 can predispose the infants for later obesity.

A risk prediction model of gestational diabetes mellitus before 16 gestational weeks in Chinese pregnant women

AIMS

To develop a GDM risk stratification model in Chinese pregnant women using machine learning algorithm, for judgment of the risk of GDM before 16 gestation weeks.

METHODS

A retrospective study of 17005 pregnant women with 1965 women developed GDM. Maternal clinical routine examination indicators, disease history and other clinical characteristics of pregnant women were obtained before 16 gestation weeks. Maternal clinical parameters were analyzed, selected and divided into 6 groups. The prediction models were constructed using LR (logistic regression) and RF (random forest), and were evaluated using areas under the receiver-operating characteristic curve (AUC). The cut-off value of the predicted probability of GDM was calculated by interquartile range. The performance of models was internal validated.

RESULTS

We developed a GDM risk stratification prediction model in Chinese pregnant women before 16 gestation weeks, with the AUC 0.746 and 15 parameters included. The model presented reliable ability to predictively stratify GDM risk of population. And the ≥ 7.77% predicted risk cut-off showed a strong ability to rule out GDM in women who predicted negative before 16 gestational weeks.

CONCLUSIONS

Our study provide a simple and effective screening method for clinical GDM risk stratification in Chinese pregnant women before 16 gestation weeks.

Vitamin B12 and Folate Levels During Pregnancy and Risk of Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis

Background: The role of vitamin B12 and folate levels with risk of gestational diabetes mellitus (GDM) is unclear. The purpose of the current study was to conduct a systematic review and meta-analysis for assessing the relationship between vitamin B12 and folate concentrations during pregnancy and the risk of GDM. Methods: PubMed, Embase, CENTRAL, and Ovid databases were searched up to 10th December, 2020 for all types of studies assessing the relationship. Qualitative and quantitative analysis of data was carried out. Results: Twelve studies were included. Pooled serum vitamin B12 concentrations were found to be significantly lower in the GDM group as compared to the non-GDM group. No such difference was noted in serum folate levels. On pooled analysis of adjusted odds ratio's for risk of GDM with red blood cell (RBC) folate, serum folate, and vitamin B12 as continuous variables, no significant relationship was seen. On qualitative analysis, studies reported higher RBC folate levels with a significantly increased risk of GDM. Majority studies reported no relationship between serum folate and risk of GDM. Four of six studies reported a lowered risk of GDM with higher or normal vitamin B12 levels. Conclusion: The association between vitamin B12 and folate levels during pregnancy and the risk of GDM is unclear. Limited number of studies indicate increased risk of GDM with higher RBC folate levels, but majority studies found no association between serum folate and risk of GDM. Based on available studies, the association between the risk of GDM with vitamin B12 deficiency is conflicting. There is a need for further large-scale studies from different regions worldwide to strengthen current evidence.

Periconceptional folate and gestational diabetes mellitus: a systematic review and meta-analysis of cohort studies

OBJECTIVE

To examine the relationship between periconceptional folate exposure and risk of gestational diabetes mellitus (GDM).

METHODS

Several electronic databases, including PubMed, Embase, China National Knowledge Infrastructure (CNKI), China Biology Medicine (CBM), and Cochrane Library, were searched for all relevant cohort studies by January 2021. Studies on relationship between folate exposure (intake or status) and GDM risk were included. Quality of included studies was assessed using Newcastle-Ottawa Scale. Random effects meta-analysis was performed to estimate overall odds ratio (OR) and 95% confidence intervals (CIs) by Stata software (Stata Corp., College Station, TX).

RESULTS

Ten cohort studies with 40,244 pregnancies were eligible for quantitative meta-analysis. Significant association was observed between folate exposure and risk of GDM (OR = 1.24, p=.036, 95% CI: 1.01-1.52). Subgroup analysis revealed that periconceptional folate exposure of population in China (OR = 1.35, 95% CI: 1.09-1.67) but not in western countries, folate exposure during pregnancy (OR = 1.49, 95% CI: 1.22-1.81) but not before pregnancy, and internal folate exposure (OR = 1.36, 95% CI: 1.10-1.67), were significantly associated with increased GDM risk.

CONCLUSIONS

Overall, periconceptional folate exposure is positively associated with GDM risk, especially the exposure during pregnancy and exposure in Chinese populations.

Association between maternal folate status and gestational diabetes mellitus

Studies on the association between maternal folate status and gestational diabetes mellitus (GDM) have yielded inconsistent results. This meta-analysis was performed to determine whether there may exist some association between maternal folate status and GDM. Unrestricted searches of PubMed, Web of Science, Cochrane, and Embase were conducted. All relevant studies on the association between maternal folat status and GDM risk were screened. The standardized mean difference (SMD) with 95% CIs was used to determine the association between maternal folate and GDM. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using random-effects models to assess the impact of maternal folate status on GDM risk. 12 studies were included. The overall data revealed that compared with the non-GDM group, women with GDM had higher level of folate (SMD 0.41, 95% CI 0.07 to 0.21, I2  = 17.2%) in second or third trimester. We also found that maternal high folate status may be associated with increased risk of GDM (OR 2.16, 95% CI 1.70 to 2.74, I2  = 0.0%). Compared with non-GDM group, women with GDM are prone to higher folate level. Moreover, high maternal folate status may predict a higher risk of GDM. As the number of included studies was limited, further large population studies are needed in the future.

The impact of micronutrient deficiency on pregnancy complications and development origin of health and disease

Due to the spread of the western style diet, which is characterized by high intake of processed food, micronutrients (vitamins and minerals) deficiency is increasing in the Japanese population of all ages and genders. During pregnancy, the elevated demand for micronutrients put pregnant women at even higher risk of micronutrients deficiency. Some micronutrients are relatively famous such that women with reproductive age are recommended to take folic acid supplementation for the prevention of neural tube defect. However, it is not generally known that folate is also important for fetal growth throughout the pregnancy course and for prevention of pregnancy complications, and that pregnant women should continue to take supplementation during pregnancy and lactation. The types of micronutrients and the duration of supplementation are both important factors to maintain normal pregnancies. This review focused on four micronutrients that are commonly deficient in Japanese pregnant women, folate, vitamin B12, vitamin D, calcium, and magnesium. The detrimental effects of homocysteine accumulation associated with the above micronutrient defects and its link to catechol-o-methyltransferase insufficiency are described. We also discussed possible molecular mechanisms of pregnancy complications and the development origin of health and disease (DOHaD) regarding micronutrient deficiencies from the point of view of one carbon metabolism.

Association of Maternal Folate and Vitamin B12 in Early Pregnancy With Gestational Diabetes Mellitus: A Prospective Cohort Study

OBJECTIVE

To investigate the association of folate and vitamin B₁₂ in early pregnancy with gestational diabetes mellitus (GDM) risk.

RESEARCH DESIGN AND METHODS

The data of this study were from a subcohort within the Shanghai Preconception Cohort Study. We included pregnancies with red blood cell (RBC) folate and vitamin B₁₂ measurements at recruitment (between 9 and 13 gestational weeks) and those with three samples available for glucose measurements under an oral glucose tolerance test. GDM was diagnosed between 24 and 28 weeks' gestation. Odds ratio (OR) and 95% CI of having GDM was used to quantify the association.

RESULTS

A total of 1,058 pregnant women were included, and GDM occurred in 180 (17.01%). RBC folate and vitamin B₁₂ were significantly higher in pregnancies with GDM than those without GDM (P values were 0.045 and 0.002, respectively) and positively correlated with 1-h and 2-h serum glucose. Daily folic acid supplementation in early pregnancy increases the risk of GDM; OR (95% CI) was 1.73 (1.19-2.53) (P = 0.004). Compared with RBC folate <400 ng/mL, pregnancies with RBC folate ≥600 ng/mL were associated with ∼1.60-fold higher odds of GDM; the adjusted OR (95% CI) was 1.58 (1.03-2.41) (P = 0.033). A significant trend of risk effect on GDM risk across categories of RBC folate was observed (P _trend = 0.021). Vitamin B₁₂ was significantly associated with GDM risk (OR 1.14 per 100 pg/mL; P = 0.002). No significant association of serum folate and percentile ratio of RBC folate/vitamin B₁₂ with GDM was observed.

CONCLUSIONS

Higher maternal RBC folate and vitamin B₁₂ levels in early pregnancy are significantly associated with GDM risk, while the balance of folate/vitamin B₁₂ is not significantly associated with GDM.

Associations Between Gestational Diabetes Mellitus Risk and Folate Status in Early Pregnancy and MTHFR C677T Polymorphisms in Chinese Women

PURPOSE

Red blood cell (RBC) folate indicates long-term folate intake, and methylenetetrahydrofolate reductase (MTHFR) gene is the main gene affecting folate status. Increasing evidence suggests an association between gestational diabetes mellitus (GDM) and increased folate levels. Whether RBC folate concentrations in the first trimester of pregnancy or polymorphisms of MTHFR C677T (rs1801133) affect GDM risk in Chinese pregnant women remains unknown. Therefore, we analyzed the associations of RBC folate concentrations and rs1801133 polymorphisms with GDM risk among pregnant women in China.

METHODS

A total of 366 women with a singleton pregnancy were followed prospectively from their first prenatal visit to delivery. RBC folate concentrations and rs1801133 polymorphisms were assessed during the first trimester of pregnancy. Binary logistic regression analyses were performed to determine the odds ratios (ORs) of GDM and 95% confidence intervals (CIs) by using the RBC folate concentration quartiles and rs1801133 polymorphisms.

RESULTS

Participants with the TT genotype had the highest RBC folate concentrations. Those with heterozygous or homozygous variants did not have a significantly higher risk of GDM than did women with C alleles. After adjustments for covariates, women in the highest quartile for RBC folate concentration had a higher risk of GDM (adjusted OR = 2.473, 95% CI = 1.013-6.037, P = 0.047) than did those in the lowest quartile, but this association was nonsignificant after adjustment for rs1801133 polymorphisms.

CONCLUSION

Higher RBC folate, partly caused by MTHFR 677C→T, may be associated with increased GDM risk, even in early pregnancy. Assessing RBC folate status and appropriately supplementing folate during early pregnancy, particularly for patients with MTHFR 677C→T, may prevent GDM. Further studies with larger populations are warranted.