Association of methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism with preterm delivery and placental abruption: a systematic review and meta-analysis

Association of methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms with vitamin B12 deficiency and adverse perinatal outcomes among pregnant women of rural South India - a cross sectional longitudinal study

OBJECTIVES

To determine the occurrence of MTHFR gene polymorphisms and to study their association with vitamin B12 deficiency and adverse perinatal outcomes among a cohort of pregnant women from Kaniyambadi block, Tamil Nadu.

METHODS

120 consecutive pregnant women who were ≤20 weeks of gestational age from the 82 villages of Kaniyambadi block were recruited. Genomic DNA was isolated from the peripheral blood. PCR amplification was done followed by Sangers sequencing. Maternal and neonatal outcomes were extracted. Data was entered and analysed.

RESULTS

Our study found the occurrence of c.1298A>C variant in homozygous state in 14.2% and c.677C>T heterozygous state in 15%. Sanger sequencing of exon 7 identified another pathogenic variant c.1262G>T in heterozygous state in two of them. Both the mothers who harboured that variant had preterm delivery and one of them gave birth to a low-birth-weight neonate. In the entire cohort, 5% of the mothers had abortion, 4.2% of them had preterm delivery and 8.8% of the neonates had low birth weight. Presence of c.1298A>C or c.677C>T variants were associated with vitamin B12 deficiency [Pearson Chi squared value (χ²)=7.9 and 7.6 respectively; p=0.02]. Heterozygous pathogenic variant c.1262G>T was associated with both adverse maternal [χ²=11.5; p=0.001] and neonatal [χ²=18.3; p=0.009] outcomes.

CONCLUSIONS

MTHFR gene polymorphisms could be associated with several adverse perinatal outcomes and vitamin B12 deficiency. Further larger studies are needed to prove the pathogenicity of c.1262G>T variant on pregnancy.

Genetic Background of Fetal Growth Restriction

Fetal growth restriction (FGR) is one of the most formidable challenges in present-day antenatal care. Pathological fetal growth is a well-known factor of not only in utero demise in the third trimester, but also postnatal morbidity and unfavorable developmental outcomes, including long-term sequalae such as metabolic diseases, diabetic mellitus or hypertension. In this review, the authors present the current state of knowledge about the genetic disturbances responsible for FGR diagnosis, divided into fetal, placental and maternal causes (including preeclampsia), as well as their impact on prenatal diagnostics, with particular attention on chromosomal microarray (CMA) and noninvasive prenatal testing technique (NIPT).

Polymorphisms in vitamin B12 and folate metabolising genes and their association with adverse pregnancy outcome: secondary analysis of a population based case control study

Vitamin B12 and folate deficiency leads to accumulation of homocysteine that increases the risk of adverse pregnancy outcomes like preterm birth and low birth weight (LBW) of the neonate. We explored the association of genetic variants of key vitamin B12 and folate metabolising enzymes (MTHFR C677T and A1298C, MTR A2756G, TCN-2 C776G) with preterm birth and LBW in South Indian women. MTHFR A1298C heterozygotes (AC) were at higher risk for preterm delivery, whereas TCN-2 C776G heterozygotes (CG) were at higher risk for both preterm delivery and LBW. MTHFR C677T, A1298C and MTR A2756G haplotype CAG was protective for preterm delivery (p=.036, OR = 0.475; 95% CI: 0.233-0.97), whereas, haplotype CCG increasing the risk of preterm birth by 1.8 folds (p=.018, OR = 1.81; 95% CI: 1.09-2.98). These results underscore the significance of vitamin B12 and folate in the pathophysiology of preterm birth and LBW.Impact StatementWhat is already known on this subject? Polymorphisms of vitamin B12 and folate metabolising genes have been reported to influence preterm birth and LBW, but the reports are not consistent.What do the results of this study add? We observed a relationship of MTHFR A1298C and TCN-2 C776G with preterm birth, and significant association of TCN-2 C776G with LBW in infants.What are the implications of these findings for clinical practice and/or further research? Identification of women carrying these polymorphic risk alleles may benefit from early nutritional modifications.

Joint Genome-Wide Association Analyses Identified 49 Novel Loci For Age at Natural Menopause

BACKGROUND

Age at natural menopause (ANM) is an important index for women's health. Either early or late ANM is associated with a series of adverse outcomes later in life. Despite being an inheritable trait, its genetic determinant has not yet been fully understood.

METHODS

Aiming to better characterize the genetic architecture of ANM, we conducted genome-wide association study (GWAS) meta-analyses in European-specific as well as trans-ancestry samples by using GWAS summary statistics from the following 3 large studies: the Reproductive Genetics Consortium (ReproGen; N = 69 626), the UK Biobank cohort (UKBB; N = 111 593) and the BioBank Japan Project (BBJ; N = 43 861), followed by a series of bioinformatical assessments and functional annotations.

RESULTS

By integrating the summary statistics from the 3 GWAS of up to 225 200 participants, this largest meta-analysis identified 49 novel loci and 3 secondary signals that were associated with ANM at the genome-wide significance level (P < 5 × 10-8). No population specificity or heterogeneity was observed at most of the associated loci. Functional annotations prioritized 90 candidate genes at the newly identified loci. Among the 26 traits that were genetically correlated with ANM, hormone replacement therapy (HRT) exerted a causal relationship, implying a causal pattern by which HRT was determined by ANM.

CONCLUSION

Our findings improved our understanding of the etiology of female menopause, as well as shed light on potential new therapies for abnormal menopause.

Folate metabolizing gene polymorphisms and genetic vulnerability to preterm birth in Korean women

BACKGROUND

The folate metabolism that converts homocysteine to methionine is closely related to the accumulation of homocysteine. Increased homocysteine levels lead to an impaired antithrombotic function of the vascular endothelium and uterine-placental circulation, resulting in abnormal pregnancy outcomes. Previous studies have reported that gene polymorphisms in folate metabolism are associated with the development of preterm birth (PTB) in various populations.

OBJECTIVE

we performed a case-control study to evaluate the association between five polymorphisms in folate metabolic genes (MTHFR, MTR, MTRR, TCN2) and PTB.

METHODS

In this study, a total of 254 subjects were analyzed (111 patients with PTB and 143 women at ≥ 38 weeks of gestation). Genotype and allele frequency differences between patients and control groups and the Hardy-Weinberg equilibrium were assessed using a Chi-square test. For evaluation indicators, odds ratios (ORs) of 95% confidence intervals (CI) were estimated. In addition, we analyzed the combined genotype frequencies of SNPs of folate-metabolizing genes to measure gene-gene interactions for PTB.

RESULTS

Our results showed that the MTR rs1805087 GG (p = 0.031), and TCN2 rs1801198 CG genotype (OR 0.53, 95% CI 0.288-0.980, p = 0.042) were significantly associated with PTB. The MTHFR rs4846049 AA showed a marginal trend toward significance (OR 0.15, 95% CI 0.018-1.205, p = 0.041). In particular, the combined genotypes, including MTHFR rs1537514 CC-MTRR rs1801394 GG, MTHFR rs1537514 CC-TCN2 rs1801198 CG, and MTR rs1805087 AA-TCN2 rs1801198 CG, have significant interactions with PTB (OR 0.49, 95% CI 0.248-0.992, p < 0.05).

CONCLUSION

The polymorphisms of folate metabolic genes may have a genetic association with the development of PTB in Korean women. A larger sample set and functional studies are required to further elucidate our findings.

Association of MTHFR 677C>T polymorphism with IUGR and placental abruption risk: A systematic review and meta-analysis

OBJECTIVE

The effects of the MTHFR 677C > T polymorphism on the intrauterine growth restriction (IUGR) and placental abruption risk have been evaluated in some studies. However, those studies results were conflicting and ambiguous. Therefore, we carried out the current meta-analysis to evaluate the association of MTHFR 677C > T polymorphism with risk of IUGR and placental abruption from all eligible studies.

METHODS

An electronic search of the PubMed, Embase, Scopus and CNKI databases was performed up to February 25, 2020.

RESULTS

A total of 25 case-control studies including eight studies with 687 cases and 2336 controls for IUGR and 17 studies with 1574 cases and 5758 controls for placental abruption were selected. The analysis results indicated that MTHFR 677C > T polymorphism was associated with an increased risk of IUGR and placental abruption in global population. When stratified by ethnicity a significant association between the MTHFR 677C > T polymorphism and IUGR risk was found in Caucasians and Africans. However, there was no a significant association between the MTHFR 677C > T polymorphism and placental abruption risk by ethnicity.

CONCLUSIONS

Our pooled data indicated that the MTHFR 677C > T polymorphism might play a role in development of IUGR and placental abruption.

Genetic variations of MTHFR gene and their association with preterm birth in Korean women

BACKGROUND AND OBJECTIVE

The MTHFR gene encodes the methylenetetrahydrofolate reductase known to be involved in the homocysteine-methionine pathway. It has been reported that the deficiency of MTHFR activity may cause hyperhomocysteinemia which results in adverse pregnancy outcomes. Previous studies reported a correlation between the MTHFR gene polymorphisms (677 T/C and 1298 A/C) and lower MTHFR activity and its association with preterm birth in various populations. Since these results were conflicting, we analyzed the genetic association of MTHFR gene 677 T/C and 1298 A/C polymorphisms with preterm birth in Korean women.

MATERIALS AND METHODS

The subjects for case-control study were collected a total of 226 Korean women (98 preterm-birth patients and 128 controls). Genotype frequency differences between the case and the control were assessed using chi-square tests. Mann-Whitney t-test was used to estimate the effects of 1298 A/C genotype on clinicopathological characteristics (systolic blood pressure, diastolic blood pressure, birth weight, and gestational age at delivery) in preterm-birth patients.

RESULTS

Our results showed that the MTHFR 677 C/T polymorphism was significantly associated with preterm-birth patients in the analysis of genotype frequency (P=0.044) and the over-dominant model (OR=0.54; 95% CI, 0.320-0.920; P=0.023). The recessive model showed a marginal trend toward significance (OR=0.47; 95% CI, 0.220-1.010; P=0.046). The 1298 A/C polymorphism was also associated with reduced preterm-birth risk in the recessive model (P=0.032). In the correlation analysis, the 1298 C allele was significantly associated with increasing of gestational age at delivery in preterm-birth patients (P=0.034).

CONCLUSIONS

Our findings suggested that the MTHFR gene 677 C/T and 1298 A/C polymorphisms might have protective effects for preterm birth in the Korean women.

Polymorphisms of methalenetetrahydrofolate reductase in recurrent pregnancy loss: an overview of systematic reviews and meta-analyses

PURPOSE

The aim is to summarize and evaluate current systematic reviews and meta-analyses on MTHFR polymorphisms in recurrent pregnancy loss (RPL).

METHODS

We searched Pubmed and Embase databases and selected in form of PICOS (participants, interventions, comparisons, outcomes, and study design). Our methodology was registered on PROSPERO (CRD42017042762). Systematic reviews and meta-analyses containing primary studies were extracted for meta-analyses, along with their OR and 95%CI. We assessed the quality of the included studies using AMSTAR and OQAQ criteria.

RESULTS

Eleven systematic reviews and meta-analyses were identified. C677T was significantly related to RPL overall in Allele (OR, 95%CI 1.43, 1.29-1.60), Recessive (OR, 95%CI 1.66, 1.42-1.95), and Homozygous (OR, 95%CI 2.08, 1.66-2.61). There was no correlation observed between A1298C and RPL, except for in Heterozygous (OR, 95%CI 1.62, 1.17-2.25).

CONCLUSIONS

We identified a difference in the association between MTHFR C677T polymorphism and RPL, especially in Asian population. No significant correlation was found between A1298C and RPL.

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.

Systematic review and meta-analysis of the associations between maternal methylenetetrahydrofolate reductase polymorphisms and preterm delivery

AIM

To date, reported associations between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and preterm delivery are conflicting. The present meta-analysis summarized the existing evidence and evaluated these associations.

METHODS

Eligible studies were retrieved from Medline (PubMed), EMBASE, the Chinese Biomedical Literature Database and the Cochrane Library. We calculated pooled odds ratios (ORs) and 95% confidence interval (CIs) within five genetic models using either random-effects or fixed-effects models dependent on study heterogeneity. Potential publication bias was assessed using a Begg's test. Sensitivity analysis was performed to evaluate the stability of the results.

RESULTS

Thirteen studies involving 4816 mothers who experienced preterm delivery and 34 506 normal controls were finally included. Significant associations between MTHFR C677T polymorphism and the risk of preterm delivery were detected overall (OR_T/C  = 1.34, 95% CI 1.12-1.61; OR_TT/CC  = 1.60, 95% CI 1.21-2.11; OR_CT/CC  = 1.33, 95% CI 1.07-1.65; OR_{TT/(CC + CT)}  = 1.41, 95% CI 1.11-1.78; OR_{(TT + CT)/CC}  = 1.36, 95% CI 1.11-1.66) and in an Asian population (OR_T/C  = 1.80, 95% CI 1.24-2.62; OR_TT/CC  = 2.13, 95% CI 1.27-3.57; OR_CT/CC  = 1.93, 95% CI 1.37-2.71; OR_{(TT + CT)/CC}  = 2.03, 95% CI 1.49-2.77). Negative associations of the A1298C polymorphism were only observed among Asian pregnant women (OR_C/A  = 0.66, 95% CI 0.50-0.88; OR_CC/AA  = 0.10, 95% CI 0.02-0.53; OR_{CC/(AA + AC)}  = 0.11, 95% CI 0.02-0.57; OR_{(CC + AC)/AA}  = 0.68, 95% CI 0.49-0.94).

CONCLUSIONS

MTHFR 677 T may play a significant role in regard to the risk of preterm delivery, especially in the Asian population.

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

PURPOSE

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.