Abstract: ObjectiveTo investigate the association of 5,10-methylenetetrahydrofolate reductase(MTHFR)’s C677T genetic point mutation with congenital heart disease(CHD) and its interaction with environmental factors.MethodsWith case-control design,104 CHD cases and 208 controls were examined.The logistic regression model was used to assess MTHFR C677T genotype variation with polymerase chain reaction restricted fragment length polymorphism(PCR-RFLP).Indicators of quantitative analysis for interaction between MTHFR gene 677TT and some of environmental factors were calculated with stratified multiplicative logistic regression model.ResultsIn the case group,the change frequency of C to T of MTHFR gene’ C667T gene was 44.24%,while the frequency was 18.75% in the control group,with a significant difference between the two groups (P<0.01).In addition,the distribution of T allele was 64.42% in the case group while it was 46.15% in the control(P<0.01).Multiple factor logistic regression analyses(α=0.05) indicated that MTHFR 677TT genetype probably was a susceptible gene (odds ratio=3.40,95% confidence interval:1.63-7.11).Seven environmental risk factors for CHD identifed were gestational hypertension,antipyretic and analgesic usage,pesticide exposure,malnutrition,low intake of vegetales,negative life event,and excessive alcohol drinking of the father with the ORs of 29.78,16.90,10.95,2.23,5.47,6.62,and 2.23,respectively.The interaction regression model analyses for the seven environmental risk factors and MTHFR 677TT genetype showed that the population attributable risks for CHD were 9.89,6.03,11.00,17.52,27.20,9.17,and 17.71,respectively.ConclusionFor patients with MTHFR 677TT genetype,the CHD incidence could be reduced by 6%-27% if seven risk factors are controlled effectively.