Roles of methylenetetrahydrofolate reductase C677T polymorphism in repeated pregnancy loss

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.

Methylenetetrahydrofolate Reductase Polymorphisms and Risk of Recurrent Pregnancy Loss: a Case-Control Study

The balance between coagulation and fibrinolysis is an essential part in early pregnancy. Mutations in methylenetetrahydrofolate reductase (MTHFR) gene lead to decreased activity of the enzyme and hyperhomocysteinemia, which then induces platelet aggregation by promoting endothelial oxidative damage, possibly resulting in adverse effect on maintenance of pregnancy. We investigated the role of MTHFR single nucleotide polymorphisms (SNPs), C677T and A1298C, in Korean patients with recurrent pregnancy loss (RPL). We conducted a prospective case-control study in the Korean population. Subjects included 302 women with 2 or more consecutive, unexplained, spontaneous miscarriages before 20 weeks of gestation and 315 control women without a history of recurrent miscarriages. The genotyping for C677T and A1298C polymorphisms was performed using the TaqMan assay. Continuous variables were compared using Student's t-test, and χ² test was used to evaluate differences in the genotype distributions between the RPL and the controls. The genotype distribution of both polymorphisms in the RPL group did not differ from those of the controls. For further analysis, if RPL patients were divided according to the numbers of pregnancy losses (≥ 2 and ≥ 3) neither group was significantly different compared with controls. MTHFR gene C677T and A1298C polymorphisms are not associated with idiopathic RPL in Korean women, suggesting that those may not be susceptible allelic variants or be deficient to cause RPL.

Comparison of two preventive treatments for patients with recurrent miscarriages carrying a C677T methylenetetrahydrofolate reductase mutation: 5-year experience

Objective

To investigate the effect of anticoagulant treatment on pregnancy outcomes in patients with previous recurrent miscarriages (RM) who carry a methylenetetrahydrofolate reductase (MTHFR) gene mutation.

Methods

In this longitudinal retrospective study, patients with RM were treated during pregnancy with either: (i) 100 mg/day aspirin and 5 mg/day folic acid (group 1); or the same protocol plus 0.4 mg/day enoxaparin (group 2). An age-matched group of triparous women without RM or thrombophilia was used as the control group (group 3).

Results

This study enrolled 246 women with RM (123 per treatment group) and age-matched controls (n = 117). The delivery rate was significantly lower in group 1 than group 2 (46.3% versus 79.7%, respectively). The miscarriage rate was significantly lower in group 2 compared with group 1 (20.3% versus 51.2%, respectively). In the control group 3, the delivery rate was 86.3% and the miscarriage rate was 12.8%.

Conclusion

Treatment with low-dose aspirin, enoxaparin and folic acid was the most effective therapy in women with RM who carried a C677T MTHFR mutation.

Thrombophilic Mutations and Polymorphisms, Alone or in Combination, and Recurrent Spontaneous Abortion

Generally, recurrent spontaneous abortions (RSAs) have no identifiable cause; yet, vascular alterations during pregnancy may be associated with pregnancy loss. Therefore, we evaluated the association between thrombophilic mutations and RSAs. This case–control study was conducted in 112 patients who had RSAs and 98 health control women. Genomic DNA was extracted from whole blood, and polymorphism genotyping was conducted using polymerase chain reaction. The following 6 genetic variants were analyzed: factor V Leiden, prothrombin mutation, methylenetetrahydrofolate reductase C677T and A1298C, plasminogen activator inhibitor type 1 (4G>5G), and factor XIII G103T (V34L). No correlations were found in any of the investigated polymorphisms. Moreover, 35.0% of cases and 25.5% of controls had at least 2 mutations in combination, and 4.8% of cases and 5.1% of controls had 3, but these combinations were not associated with additional risk. In conclusion, we found no association between the polymorphisms studied and the occurrence of RSAs.

Association study between methylenetetrahydrofolate reductase polymorphisms and unexplained recurrent pregnancy loss: a meta-analysis

BACKGROUND

Recurrent pregnancy loss is an important clinical problem. Recently, high-level homocysteine in blood has been considered as a possible cause. Genetic polymorphisms in methylenetetrahydrofolate reductase (MTHFR) have been proved to be the common hereditary factors of high-level homocysteine. The association between MTHFR polymorphisms and unexplained recurrent pregnancy loss (URPL) has been reported but with controversial results. The purpose of present study is to collect and analyze published available data, and evaluate the association between MTHFR polymorphisms and URPL.

METHODS

A meta-analysis was performed to examine the association between MTHFR polymorphisms (C677T and A1298C) and URPL. Odds ratio (OR) and its 95% confidence interval (CI) were used in each study of genotype and allele contrast.

RESULT(S)

MTHFR C677T: The analysis included 3559 URPL cases and 5097 healthy controls. Overall random-effects odds ratios (ORs) were 1.68 (95% CI, 1.32-2.13; P<0.0001) for TT versus total genotypes, 1.35 (95% CI, 1.04-1.76; P=0.0224) for TT and CT genotype combined versus total genotypes and 1.34 (95%CI, 1.13-1.58; P<0.0001) for T versus total alleles. Although significant heterogeneity was found in C677T, it became weaker in the East Asian subgroup and the mixed subgroup when separated by ethnic subgroups. The results showed significant association between MTHFR C677T and URPL in the East Asian subgroup (ORs 2.11 for TT versus total genotype (P=0.0004) and 1.53 for T versus total alleles (P<0.0001)) and in the mixed subgroup (ORs 3.47 for TT versus total genotypes (P<0.0001) and 1.80 for T versus total alleles (P<0.027)), but not in Caucasian subgroup. MTHFR A1298C: The study involved 1163 URPL cases and 1061 healthy controls. Overall random-effects odds ratios (ORs) were 1.37 (95% CI, 0.71-2.67; P=0.3456) for CC versus total genotypes, 1.16 (95%CI, 0.98-1.38; P=0.0833) for CC+AC versus total genotypes and 1.04 (95%CI, 0.84-1.29; P=0.7112) for C versus total alleles. No significant association between MTHFR A1298C polymorphism and URPL was found.

CONCLUSIONS

These results indicate a significant association between MTHFR C677T mutation and URPL in the East Asian subgroup and mixed subgroup, but no significance in MTHFR A1298C mutation.