Maternal Methylenetetrahydrofolate Reductase C677T Research Articles

Association of Methylenetetrahydrofolate Reductase Gene Polymorphism C677T with Oocyte Number and Embryo Quality in Iraqi Infertile Women Undergoing Intracytoplasmic Sperm Injection

Background: Methylenetetrahydrofolate reductase (MTHFR) C677T is a single nucleotide polymorphism (SNP) that affects the production of 5-methyltetrahydrofolate (5-MTHF), the active folate that enables the recycling of homocysteine (Hcy) to methionine. Objective: to investigate the association between the MTHFR (C677T) polymorphism and the outcomes of intracytoplasmic sperm injection (ICSI). Methods: A prospective cohort study included 85 infertile women undergoing ICSI treatment at the High Institute of Infertility Diagnosis and Assisted Reproductive Technologies in Baghdad, Iraq. The study period extended from January 2022 to September 2023. The MTHFR C677T polymorphism genotyping was evaluated in these patients, and they were classified into three groups according to genotyping results: normal (CC), heterozygote mutated (CT), and mutated homozygote (TT). In addition, we conducted a comparative analysis of oocyte, embryo and pregnancy rates among these three groups. Results: In comparison to the CT and TT genotypes, the total number of oocytes, total embryos, mature oocytes, good-quality embryos, and pregnancy rate were all found to be significantly higher (p<0.05) in the CC genotype. Compared to the CC group, the proportion of immature oocytes and poor-quality embryos was significantly higher in the TT and CT groups (p<0.05). The rate of fertilization was comparable among the study groups. Conclusions: The maternal MTHFR C677T polymorphism is linked to oocyte number, maturity, total embryo, embryo quality, and pregnancy in ICSI. In light of this, MTHFR polymorphism in our community offers useful data regarding the success of ICSI.

Association of Methylenetetrahydrofolate Reductase Gene Polymorphism in Mothers With Adverse Clinical Outcomes in Neonates.

The presence of polymorphic methylenetetrahydrofolate reductase(MTHFR) in mothers poses a risk for numerous detrimental outcomes in neonates. The present study investigated the association of maternal MTHFR A1298C and C677T single nucleotide polymorphisms (SNPs) with the clinical outcomes in their neonates. The cross-sectional study included 60 mothers and their neonates. Blood samples from mothers were analyzed for MTHFR A1298C and C677T SNP genotyping by real-time polymerase chain reaction. Clinical details of mothers and neonates were documented. Study groups were stratified based on wild, heterozygous, and mutant genotypes for the respective polymorphisms observed in mothers. Multinomial regression was applied for the association, followed by gene model formulation to estimate the impact of the genetic variants on the outcomes. The frequency percentages of mutant CC1298 and TT677 genotypes were 25% and 8.06%, respectively, and the mutant allele frequencies (MAF) were 42.5% and 22.5%. Percentages of adverse outcomes such as intrauterine growth restriction, sepsis, anomalies, and mortality were higher in neonates born to mothers with homozygous mutant genotypes. Maternal C677T MTHFR SNPs revealed a significant association with neonatal anomalies (p = 0.001). The multiplicative risk model depicted OR (95% CI) for CT vs. CC+TT as 3.0 (95% CI: 0.66-13.7), and for TT vs. CT+CC was 15 (95% CI: 2.01-112.12). The C677T SNP in mothers predicted a dominant model for neonatal death (OR (95% CI): 5.84 (0.57-60.03), p = 0.15), whereas the A1298C reported recessive model for 1298CC mothers (OR (95% CI): 11 (1.05-115.5), p = 0.02). Both the genotypes assumed a recessive model for adverse neonatal outcomes: OR (95%CI) for CC vs. AA+ACwas 3.2 (0.79-12.9, p = 0.1), and for TT vs. CC+CT was 5.48 (0.57-175.7, p = 0.2). The risk for sepsis in neonates was nearly six times higher in those born from mothers with homozygous CC1298 and TT677 than in the wild and heterozygous variants. Mothers with C677T and A1298C SNPs are highly susceptible to adverse outcomes in their neonates. Hence, screening the SNPs during the antenatal period can purposefully serve as a better predictive marker, following which proper clinical management could be planned.

MTHFR C677T POLYMORPHISM: A MATERNAL RISK FACTOR FOR HAVING A MENTALLY RETARDED CHILD IN INDIA

The present case-control study examined the association of genetic polymorphism with mental retardation. One common polymorphism (SNPs), C677T in the 5,10- methylenetetrahydrofolate reductase (MTHFR) gene involved in folate metabolism, is known to lower the activity of this enzyme. One hundred sixty mothers (with MR and normal children), from the Eastern Uttar Pradesh, India, were genotyped for MTHFR C677T SNP. Significant association with this SNP was detected, more specifically, with T allele in the mothers of MR children. The relative risk of T (C677T) in mothers for MR-affected pregnancy was 3 (OR 3.179, 95% CI 1.40-7.78). The results indicated statistically significant associations between maternal MTHFR C677T polymorphism and congenital heart defects in foetus under different genetic models.

Study on the polymorphism of methylenetetrahydrofolate reductase C677T gene as the genetic predisposition of congenital heart disease in North Indian population

Background: The etiology of congenital heart disease (CHD) is still not known properly. The variant alleles in the methylenetetrahydrofolate reductase (MTHFR) C677T gene help in elevating the serum homocysteine level which is an independent predisposing factor for generating CHD. Aims and Objectives: The aim of the present study was to analyze the role of polymorphism of MTHFR C677T gene polymorphisms in CHD patients of Varanasi, Uttar Pradesh, North India. Materials and Methods: The present study included 36 unrelated CHD patients along with their parents. At the same time, 40 healthy control samples were included in the study. MTHFR 677 C>T genotype was identified by polymerase chain reaction followed by restriction digestion restriction fragment length polymorphism mechanism. Results: There was a significant difference observed in MTHFR C677T gene polymorphism between the cases and controls (P<0.001). Among the different etiological factors, increased maternal age, family history, and teratogens are the major ones. Maternal MTHFR C677T genotype and periconceptional folate intake have important ascription toward CHD formation. Conclusion: The results designate that MTHFR C677T polymorphism has a substantial association with the development and progression of CHDs. Folate supplementation might be the probable management strategy for reducing the risk of CHDs as maternal MTHFR C677T polymorphism has an important contribution.

Association between Maternal and Fetal MTHFR C677T and MTRR A66G Polymorphisms with the Risk of NTDs: A Systematic Review and Meta-Analysis Study

Background: Neural tube defects (NTDs) are classed as multifactorial birth defects of the brain and spinal cord that arise during embryonic development. Although the etiology is not well understood, NTDs are reported to be prevented by maternal folic acid supplementation before and during early pregnancy. This meta-analysis study aimed to assess the association between fetal and maternal methylenetetrahydrofolate reductase (MTHFR) C677T and methionine synthase reductase (MTRR) A66G polymorphisms with the risk of NTDs. Methods: The PubMed, Scopus, and Springer Link databases were searched (from March 2000 to November 2020) for the literature on the association between MTHFR C677T and MTRR A66G polymorphisms with the risk of NTDs. Results: In total, 33 studies were reviewed in the present study, and it was revealed that, unlike MTRR A66G polymorphism, MTHFR C677T was statistically associated with the risk of NTDs in the overall population. The results of subgroup analysis showed that the Indian subcontinent subgroup with maternal MTHFR C677T polymorphism and the European subgroup with fetal MTHFR C677T polymorphism was significantly susceptible to NTDs. Conclusion: The obtained results revealed that, unlike MTRR A66G, maternal and fetal MTHFR C677T polymorphism was significantly associated with NTDs. Subgroup analysis also demonstrated that folic acid deprivation can be considered the main cause of MTHFR C677T polymorphism in some areas.

Prenatal Multivitamin Use and MTHFR Genotype Are Associated with Newborn Cord Blood DNA Methylation.

Background: Fetal development involves cellular differentiation and epigenetic changes—complex processes that are sensitive to environmental factors. Maternal nutrient levels during pregnancy affect development, and methylene tetrahydrofolate reductase (MTHFR) is important for processing the nutrient folate. Hypothesis: We hypothesize that supplement intake before pregnancy and maternal genotype are associated with DNA methylation in newborns. Methods: In the pregnancy cohort, Early Autism Risk Longitudinal Investigation (EARLI), health history, and genotype information was obtained (n = 249 families). Cord blood DNA methylation (n = 130) was measured using the Illumina HumanMethylation450k array and global DNA methylation levels were computed over 455,698 sites. Supplement use preconception and during pregnancy were surveyed at visits during pregnancy. We evaluated associations between maternal preconception supplement intake and global DNA methylation or DNA methylation density distributions of newborn cord blood, stratified by the presence of a variant maternal MTHFR C677T allele. Results: Maternal preconceptional multivitamin intake was associated with cord blood methylation, dependent on maternal MTHFR genotype (interaction term p = 0.013). For mothers without the MTHFR variant allele, multivitamin intake was associated with 0.96% (95% CI: 0.09, 1.83) higher global cord blood methylation (p = 0.04) and was also associated with the cumulative density distribution of methylation (p = 0.03). For mothers with at least one variant allele, multivitamin intake had a null −0.06% (95% CI: −0.45, 0.33) association with global cord blood DNA methylation, and was not associated with the cumulative density distribution (p = 0.37). Conclusions: We observed that cord blood DNA methylation was associated with maternal supplement exposure preconception and maternal genotype. Genetic context should be considered when assessing DNA methylation effects of modifiable risk factors around the time of pregnancy.

The association between maternal methylenetetrahydrofolate reductase C677T and A1298C polymorphism and birth defects and adverse pregnancy outcomes.

Published studies indicate the MTHFR C677T and A1298C polymorphisms are associated with abnormal homocysteine levels, which may cause various pregnancy complications and birth defects. However, the results obtained from different studies have been inconsistent. Therefore, this meta-analysis explores the association between MTHFR polymorphisms and birth defects and adverse pregnancy outcomes. The PubMed, ScienceDirect, Embase, and China Biology Medicine literature databases and ClinicalTrials were searched. Analyses of public bias, meta-regression, subgroups, and sensitivity were used to ensure the robustness of our results. MTHFR C677T was significantly associated with recurrent pregnancy loss in developing countries (odds ratio [OR], 1.34; 95% confidence interval [CI], 1.20-1.50) but not in developed countries (OR, 0.87; 95% CI, 0.68-1.11). No significant relationship was found between MTHFR A1298C and recurrent pregnancy loss (OR, 1.04; 95% CI, 0.93-1.18). MTHFR C677T and A1298C were not associated with preeclampsia (OR, 1.06; 95% CI, 0.97-1.16 and OR, 1.16; 95% CI, 0.97-1.39, respectively), and C677T was not associated with placental abruption (OR, 1.03; 95% CI, 0.87-1.21), intrauterine growth retardation (OR, 1.02; 95% CI, 0.90-1.15), or congenital heart disease (OR, 1.05; 95% CI, 0.89-1.25). MTHFR C677T, but not A1298C, was associated with neural tube defects (OR, 1.24; 95% CI, 1.08-1.42) and Down syndrome (OR, 1.65; 95% CI, 1.39-1.95). CONCLUSION: Although MTHFR C677T and A1298C are significantly associated with some types of congenital defects and adverse pregnancy outcomes, the impact of these polymorphisms is moderate.

Low maternal folate concentrations and maternal MTHFR C677T polymorphism are associated with an increased risk for neural tube defects in offspring: a case-control study among Pakistani case and control mothers.

There is considerable evidence that periconceptional maternal folate deficiency and coding variants in maternal genes coding for critical enzymes in the folate pathway are associated with neural tube defects (NTDs) in offspring. In a case-control study we investigated C677T polymorphism in the 5,10- methylenetetrahydrofolate reductase (MTHFR) gene in case and control mothers of Pakistani origin, and compared these with the respective maternal folate concentrations measured at the time of delivery. A case-control study was conducted among 109 case and 100 control mothers identified through the Holy Family Hospital Rawalpindi, Quaid-i-Azam University, Islamabad, Pakistan. Red blood cell (RBC) and serum folate concentrations and MTHFRC677T polymorphism were compared between case and control mothers. Mean RBC folate and serum folate concentrations were significantly lower in cases compared with control mothers (p<0.0001). Maternal MTHFR 677CT and 677TT genotypes were more common among cases compared with control mothers (CC vs TT p<0.0393 and CC/CT vs TT p<0.021). T-allele frequency was higher in cases compared with control mothers (C vs T p<0.017). Case mothers with 677CT or 677TT genotypes had significantly lower serum (p<0.0001) and RBC folate concentrations (p<0.0001) compared with control mothers. The present study provides further evidence that maternal folate deficiency and MTHFRC677T polymorphism might be associated with an increased risk for NTDs in offspring. Our results are limited by the fact that maternal folate concentrations were not obtained during the periconceptional period, but at delivery. Further analyses, including maternal folate levels during the periconceptional period, are warranted.

Genetic polymorphism of MTHFR C677T with preterm birth and low birth weight susceptibility: a meta-analysis.

This study aimed at clarifying the association of maternal and neonatal methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms with preterm birth (PTB) and low birth weight (LBW) susceptibility, respectively. A systematic search of Embase, Medline, China Biological Medicine Database (CBM), Chinese National Knowledge Infrastructure (CNKI), and Wanfang Database was performed before June, 2016. The frequencies of maternal and neonatal MTHFR C677T genotypes in the cases and controls and other information were extracted by two independent investigators. Odds ratios (ORs) with 95% confidence intervals (CIs) were adopted to estimate the relationships between MTHFR C677T polymorphisms and PTB as well as LBW by random or fixed effect models. Twenty-five studies from 20 articles concerning maternal and neonatal MTHFR C677T gene polymorphism with PTB and LBW were included in this study. Maternal MTHFR C677T polymorphism was associated with PTB risk under allele contrast (T vs. C, OR = 1.36, 95% CI 1.02-1.81), homozygote (TT vs. CC, OR = 1.70, 95% CI 1.07-2.68), and recessive (TT vs. CT + CC, OR = 1.49, 95% CI 1.00-2.22) model, but not dominant or heterozygote model. Maternal MTHFR C677T polymorphism was also associated with LBW risk under allele contrast (OR = 1.69, 95% CI 1.25-2.28), homozygote (OR = 2.26, 95% CI 1.44-3.54), dominant (OR = 1.71, 95% CI 1.19-2.47), recessive (OR = 1.79, 95% CI 1.42-2.26) model, but not heterozygote model. No associations between neonatal MTHFR C677T polymorphism and PTB or LBW were found under all genetic models. Identification of maternal MTHFR C677T mutation may play a key role for primary prevention of PTB as well as LBW and screening pregnant women of high risk in developing countries.

Association between Maternal MTHFR Polymorphisms and Nonsyndromic Cleft Lip with or without Cleft Palate in Offspring, A Meta-Analysis Based on 15 Case-Control Studies.

The methylenetetrahydrofolate reductase (MTHFR) is thought to be involved in the development of nonsyndromic cleft lip with or without cleft palate (NSCL/P). However, conflicting results have been obtained when evaluating the association between maternal MTHFR C677T and A1298C polymorphisms and the risk of NSCL/P. In light of this gap, a meta-analysis of all eligible case-control studies was conducted in the present study. A total of 15 case-control studies were ultimately identified after a comprehensive literature search and Hardy-Weinberg equilibrium (HWE) examination. Cochrane's Q test and index of heterogeneity (I(2)) indicated no obvious heterogeneity among studies. Fixed or random-effects models were used to calculate the pooled odds ratios (ORs). The results showed that the TT genotype in mothers increased the likelihood of having NSCL/P offspring 1.25 times (95% CI: 1.047-1.494) more than the CC homozygotes. Meanwhile, maternal TT genotype increased the risk of producing NSCL/P offspring in recessive model (OR=1.325, 95% CI: 1.124-1.562). However, the CT heterozygote and the CT+TT dominant models had no association with NSCL/P offspring compared with the CC wild-type homozygote model. Subgroup analyses based on ethnicity indicated that maternal TT genotype increased the likelihood of having NSCL/P offspring in Whites (OR=1.308, 95% CI: 1.059-1.617) and Asians (OR=1.726, 95% CI: 1.090-2.733) in recessive model. Also, subgroup analyses based on source of control showed that mothers with the 677TT genotype had a significantly increased susceptibility of having NSCL/P children in hospital based population (HB) when compared with CC homozygotes (OR=1.248, 95% CI: 1.024-1.520) and un- der the recessive model (OR=1.324, 95% CI: 1.104-1.588). Furthermore, maternal A1298C polymorphism had no significant association with producing NSCL/P offspring (dominant model OR=0.952, 95% CI: 0.816-1.111, recessive model OR=0.766, 95% CI: 0.567-1.036). MTHFR C677T polymorphism is associated with the risk of generating NSCL/P offspring, and being a 677TT homozygote is a risk factor. MTHFR A1298C polymorphism was not associated with generating NSCL/P offspring. However, further work should be performed to confirm these findings.

Maternal methylenetetrahydrofolate reductase C677T polymorphism and down syndrome risk: a meta-analysis from 34 studies.

BackgroundMethylenetetrahydrofolate reductase (MTHFR) is a key enzyme of folate metabolic pathway which catalyzes the irreversible conversion of 5, 10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. 5-methyltetrahydrofolate donates methyl group for the methylation of homocysteine to methionine. Several studies have investigated maternal MTHFR C677T polymorphism as a risk factor for DS, but the results were controversial and inconclusive. To come into a conclusive estimate, authors performed a meta-analysis.AimA meta-analysis of published case control studies was performed to investigate the association between maternal MTHFR C677T polymorphism and Down syndrome.MethodsPubMed, Google Scholar, Elsevier, Springer Link databases were searched to select the eligible case control studies using appropriate keywords. The pooled odds ratio (OR) with 95%confidence interval were calculated for risk assessment.ResultsThirty four studies with 3,098 DS case mothers and 4,852 control mothers were included in the present meta-analysis. The pooled OR was estimated under five genetic models and significant association was found between maternal MTHFR 677C>T polymorphism and Down syndrome under four genetic models except recessive model (for T vs. C, OR = 1.26, 95% CI = 1.09–1.46, p = 0.001; for TT vs. CC, OR = 1.49, 95% CI = 1.13–1.97, p = 0.008; for CT vs. CC, OR = 1.29, 95% CI = 1.10–1.51, p = 0.001; for TT+CT vs. CC, OR = 1.35, 95% CI = 1.13–1.60, p = 0.0008; for TT vs. CT+CC, OR = 0.76, 95% CI = 0.60–0.94, p = 0.01).ConclusionThe results of the present meta-analysis support that maternal MTHFR C677T polymorphism is a risk factor for DS- affected pregnancy.

"Polymorphisms in folate metabolism genes as maternal risk factor for neural tube defects: an updated meta-analysis".

Epidemiological studies have evaluated the association between maternal methylenetetrahydrofolate reductase (MTHFR) C677T, A1298C and methionine synthase reductase (MTRR) A66G polymorphisms and risk of neural tube defects (NTDs) in offspring. However, the results from the published studies on the association between these three polymorphisms and NTD risk are conflicting. To derive a clearer picture of association between these three maternal polymorphisms and risk of NTD, we performed meta-analysis. A comprehensive search was conducted to identify all case-control studies of maternal MTHFR and MTRR polymorphisms and NTD risk. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association. Overall, we found that maternal MTHFR C677T polymorphism (OR(TvsC) =1.20; 95% CI = 1.13-1.28) and MTRR A66G polymorphism (OR(GvsA) = 1.21; 95% CI = 0.98-1.49) were risk factors for producing offspring with NTD but maternal MTHFR A1298C polymorphism (OR(CvsA) = 0.91; 95% CI = 0.78-1.07) was not associated with NTD risk. However, in stratified analysis by geographical regions, we found that the maternal C677T polymorphism was significantly associated with the risk of NTD in Asian (OR(TvsC) = 1.43; 95% CI: 1.05-1.94), European (OR(TvsC) = 1.13; 95% CI: 1.04-1.24) and American (OR(TvsC) = 1.26; 95% CI: 1.13-1.41) populations. In conclusion, present meta-analysis supports that the maternal MTHFR C677T and MTRR A66G are polymorphisms contributory to risk for NTD.

No major role for periconceptional folic acid use and its interaction with the MTHFR C677T polymorphism in the etiology of congenital anorectal malformations.

Both genetic and nongenetic factors are suggested to be involved in the etiology of congenital anorectal malformations (ARM). Maternal periconceptional use of folic acid supplements were inconsistently suggested to play a role in the prevention of ARM. Therefore, we investigated independent associations and interactions of maternal periconceptional folic acid supplement use and the infant and maternal MTHFR (methylenetetrahydrofolate reductase) C677T polymorphisms with the risk of ARM and subgroups of ARM. A case-control study was conducted among 371 nonsyndromic ARM cases and 714 population-based controls born between 1990 and 2012 using maternal questionnaires and DNA samples from mother and child. Cases were treated for ARM at departments of Pediatric Surgery of the Radboud university medical center, Sophia Children's Hospital-Erasmus MC Rotterdam, and the University Medical Center Groningen in The Netherlands and hospitals throughout Germany. No association with folic acid use was present (odds ratio = 1.1; 95% confidence interval: 0.8-1.4) for ARM as a group. Infant and maternal MTHFR C677T polymorphisms were weakly associated with isolated ARM in particular. Lack of folic acid supplement use in combination with infants or mothers carrying the MTHFR C677T polymorphism did not seem to increase the risk of ARM or subgroups of ARM. The relative excess risks due to interaction did not clearly indicate interaction on an additive scale either. This first study investigating interactions between periconceptional folic acid supplement use and infant and maternal MTHFR C677T polymorphisms in the etiology of ARM did not provide evidence for a role of this gene-environment interaction.

Association between 5, 10-methylenetetrahydrofolate reductase (MTHFR) polymorphisms and congenital heart disease: A meta-analysis

BackgroundInconsistent results were reported in recent literature regarding the association between methylenetetrahydrofolate reductase (MTHFR) C677T/A1298C polymorphisms and the susceptibility of congenital heart disease (CHD). In this study, we performed a meta-analysis to investigate the associations by employing multiple analytical methods. MethodsLiterature search was performed and published articles were obtained from PubMed, Embase and CNKI databases based on the exclusion and inclusion criteria. Data were extracted from eligible studies and the crude odds ratios and their corresponding 95% confidence intervals (CIs) were calculated using random or fix effects model to evaluate the associations between the MTHFR C677T/A1298C polymorphisms and CHD development. Subgroup based analysis was performed by Hardy–Weinberg equilibrium, ethnicity, types of CHD, source of control and sample size. ResultsTwenty-four eligible studies were included in this meta-analysis. Significant association was found between fetal MTHFR C677T polymorphism and CHD development in all genetic models. The pooled ORs and 95% CIs in all genetic models indicated that MTHFR C677T polymorphism was significantly associated with CHD in Asian, but not Caucasian in subgroup analysis. The maternal MTHFR C677T polymorphism was not associated with CHD except for recessive model. Moreover, neither maternal nor fetal MTHFR A1298C polymorphism was associated with CHD. ConclusionThe fetal MTHFR C677T polymorphism may increase the susceptibility to CHD. Fetal MTHFR C677T polymorphism was more likely to affect Asian fetus than Caucasian. The MTHFR A1298C polymorphism may not be a risk of congenital heart disease.

Maternal MTHFR C677T genotype and septal defects in offspring with Down syndrome: A pilot study

BackgroundWhile abnormal folate/homocysteine metabolism has been implicated as an etiology for the development of both CHD and DS, recent studies and meta-analyses did not consider MTHFR C677T genotype as a maternal risk factor for either of these conditions alone. Aim of workTo investigate if methylenetetrahydrofolate reductase (MTHFR) C677T genotype is a maternal risk factor for the development of congenital heart disease (CHD) only in children with Down syndrome (DS). Subjects and methodsMolecular analysis of MTHFR C677T and serum folic acid was done for sixty-one consecutive mothers of children with CHD in the form of septal defects (26 with DS and 35 without DS) and another 61 mothers of apparently healthy children (without DS or CHD). ResultsThe frequency of CT genotype was significantly higher in mothers of children with AV canal (whether in DS or non-DS) when compared to ASD and in mothers of DS with AV canal when compared to controls. The frequency of TT genotype was higher in mothers of DS with ASD than controls but statistically insignificant. In non-DS mothers, the distribution of the genotypes did not differ in relation to the type of CHD. The mean folic acid level did not differ between different study groups. ConclusionsMTHFR 677CT genotype could be implicated as a maternal risk factor for septal defects especially in children with DS. Carriers of this genotype may have more risk of development of AV canal in their children. A major limitations of this study was the small sample size and so further studies on a larger sample of patients and their mothers in addition to measurement of homocysteine level in this population is needed to investigate this theory and to clarify the actual role of MTHFR polymorphism and the risk of development of CHD in DS.

Maternal gene polymorphisms involved in folate metabolism and the risk of having a Down syndrome offspring: a meta-analysis

Down syndrome (DS) is the most common chromosomal abnormality. Many studies have assessed the association between maternal gene polymorphisms involved in folate metabolism and the risk of having a DS offspring, but data are conflicting. Our study aimed to arrive at a more accurate estimation. Therefore, we carried out a meta-analysis of 26, 17, 9, 15, 9 and 6 case-control studies on the relationship between maternal methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, methionine synthase (MTR) A2756G, methionine synthase reductase (MTRR) A66G, reduced folate carrier 1 A80G and cystathionine β-synthase 844ins68 polymorphisms and the risk of having a DS offspring. The allele contrast and model-free approach were used. Results showed marginal significant associations for MTHFR C677T, overall [odds ratio (OR) = 1.28 (1.22, 1.46) and generalised odds ratio (ORG) = 1.35 (1.16, 1.57)] and in Caucasian [OR = 1.15 (1.03, 1.29) and ORG = 1.20 (1.04, 1.38)], Asian [OR = 1.68 (1.08, 2.63) and ORG = 1.74 (1.08, 2.80)] and Brazilian [OR = 1.22 (1.04, 1.43) and ORG = 1.28 (1.06, 1.55)] populations; for MTRR A66G, overall [OR = 1.22 (1.02, 1.46) and ORG = 1.31 (1.06, 1.62)]; and for RFC1 A80G, overall [OR = 1.16 (1.02, 1.31) and ORG = 1.18 (1.01, 1.37)]. MTHFR A1298C, MTR 12756G and CBS 844ins68 polymorphisms produced non-significant results. Since potential confounders could not be ruled out completely in this meta-analysis, further studies are needed to confirm these results.

MTHFR C677T polymorphism and risk of congenital heart defects: evidence from 29 case-control and TDT studies.

BackgroundMethylenetetrahydrofolate reductase (MTHFR) is an important enzyme for folate metabolism in humans; it is encoded by the MTHFR gene. Several studies have assessed the association between MTHFR C677T polymorphism and the risk of congenital heart defects (CHDs), while the results were inconsistent.Methods and FindingsMultiple electronic databases were searched to identify relevant studies published up to July 22, 2012. Data from case-control and TDT studies were integrated in an allelic model using the Catmap and Metafor software. Twenty-nine publications were included in this meta-analysis. The overall meta-analysis showed significant association between MTHFR C677T polymorphism and CHDs risk in children with heterogeneity (P heterogeneity = 0.000) and publication bias (P egger = 0.039), but it turned into null after the trim-and-fill method was implemented (OR = 1.12, 95% CI = 0.95–1.31). Nevertheless, positive results were obtained after stratified by ethnicity and sample size in all subgroups except the mixed population. For mothers, there was significant association between the variant and CHDs without heterogeneity (P heterogeneity = 0.150, OR = 1.16, 95% CI = 1.05–1.29) and publication bias (P egger = 0.981). However, the results varied across each subgroup in the stratified analysis of ethnicity and sample size.ConclusionsBoth infant and maternal MTHFR C677T polymorphisms may contribute to the risk of CHDs.

Mendelian Randomization Analysis of the Effect of Maternal Homocysteine During Pregnancy, as Represented by Maternal MTHFR C677T Genotype, on Birth Weight

BackgroundWe used Mendelian randomization analysis to investigate the causal relationship between maternal homocysteine level, as represented by maternal methylenetetrahydrofolate reductase (MTHFR) C677T genotype, with the birth weight of offspring.MethodsWe recruited women at 24 to 28 weeks’ gestation who visited Ewha Womans University Hospital for prenatal care during the period from August 2001 to December 2003. A total of 473 newborns with a gestational age of at least 37 weeks were analyzed in this study. We excluded twin births and children of women with a history of gestational diabetes, gestational hypertension, or chronic renal disease. The association of maternal homocysteine concentration with the birth weight of infants was analyzed using 2-stage regression.ResultsMTHFR C677T genotype showed a dose–response association with homocysteine concentration for each additional T allele (Ptrend < 0.01). Birth weight decreased from 120 to 130 grams as maternal homocysteine level increased, while controlling for confounding factors; however, the association was of marginal significance (P = 0.06).ConclusionsOur results suggest an adverse relationship between maternal homocysteine level and birth weight. A reduction in homocysteine levels might positively affect birth outcomes.

Maternal MTHFR C677T polymorphism and congenital heart defect risk in the Chinese Han population: a meta-analysis

Numerous studies have evaluated the association between the maternal C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene and congenital heart defect (CHD) risk in the Chinese Han population. However, the specific association is still controversial. Six separate studies with 1089 subjects in the Chinese Han population on the relationship between the C677T polymorphism and CHDs were analyzed by meta-analysis, upon database search. The fixed-effect model or random-effect model was selected to calculate the pooled odds ratio (ORs) and its corresponding 95% confidence interval (95%CI) when appropriate. The Begg test was used to measure publication bias. Sensitivity analyses were performed to insure authenticity of the outcome. Meta-analysis of the results showed significant associations between the maternal C677T polymorphism and CHD risk (CC vs TT: OR = 0.65, 95%CI = 0.44-0.96). Limiting the analysis to the studies with controls in the Hardy-Weinberg equilibrium and the results indicate that the meta-analysis was statistically significant. Results of Begg's funnel plot showed that there was no publication bias (all P > 0.05). The present meta-analysis suggested that the maternal C677T polymorphism is a risk factor for CHDs in the Chinese Han population.

Association of the Maternal MTHFR C677T Polymorphism with Susceptibility to Neural Tube Defects in Offsprings: Evidence from 25 Case-Control Studies

BackgroundMethylenetetrahydrofolate reductase (MTHFR) is a critical enzyme in folate metabolism and is involved in DNA methylation, DNA synthesis, and DNA repair. In addition, it is a possible risk factor in neural tube defects (NTDs). The association of the C677T polymorphism in the MTHFR gene and NTD susceptibility has been widely demonstrated, but the results remain inconclusive. In this study, we performed a meta-analysis with 2429 cases and 3570 controls to investigate the effect of the MTHFR C677T polymorphism on NTDs.MethodsAn electronic search of PubMed and Embase database for papers on the MTHFR C677T polymorphism and NTD risk was performed. All data were analysed with STATA (version 11). Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated to assess the association. Sensitivity analysis, test of heterogeneity, cumulative meta-analysis, and assessment of bias were performed in our meta-analysis.ResultsA significant association between the MTHFR C677T polymorphism and NTD susceptibility was revealed in our meta-analysis ( TT versus CC: OR = 2.022, 95% CI: 1.508, 2.712; CT+TT versus CC: OR = 1.303, 95% CI: 1.089, 1.558; TT versus CC+CT: OR = 1.716, 95% CI: 1.448, 2.033; 2TT+CT versus 2CC+CT: OR = 1.330, 95% CI: 1.160, 1.525). Moreover, an increased NTD risk was found after stratification of the MTHFR C677T variant data by ethnicity and source of controls.ConclusionThe results suggested the maternal MTHFR C677T polymorphism is a genetic risk factor for NTDs. Further functional studies to investigate folate-related gene polymorphisms, periconceptional multivitamin supplements, complex interactions, and the development of NTDs are warranted.