Background: The 5, 10-methyleneterahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) are two essential enzymes involved in folate metabolism. The relationship between genetic polymorphisms and congenital heart defects (CHDs) is inconsistent. Our aim was to investigate the association between two well-known polymorphisms of MTHFR and MTRR genes, C677T and A66G, respectively, and CHDs in Iranian patients.

Methods: We enrolled 74 patients with ventricular septal defect (VSD) and 79 with tetralogy of fallot (TOF) along with 147 healthy controls. C677T and A66G polymorphisms were detected using tetra-primer ARMS (amplification refractory mutation system) PCR.

Results: Individuals carrying homozygote mutant (TT) genotype of C677T polymorphism represented the highest risk for CHDs (OR=7.3, 95% CI: 0.8-61, P=0.06). Also, significantly increased risk of VSD was observed in individuals with TT genotype (OR=10, 95% CI: 1-92.2, P=0.04). However, the frequency for variant allele (T) of C677T polymorphism was not statistically different between cases and controls (16.3% and 20.9%, respectively). For A66G polymorphism, we found that AG and GG genotypes had higher frequencies in the patients (48.4% and 21.6% respectively) than controls (42.9% and 15.6%, respectively). In line with this, combined AG+GG genotype represented with significantly elevated risk of CHDs (OR=1.6; 95% CI: 1-2.6, P=0.03). AG+GG combination was also identified as a risk factor for TOF (OR=1.8, 95% CI: 1-3.3, P=0.04).

Conclusion: We demonstrated that C677T polymorphism of MTHFR gene was significantly associated with VSD in our patients. Our study also suggested that A66G polymorphism of MTRR gene may contribute to the development of TOF in Iranians.