OBJECTIVETo investigate the correlationship between congenital heart disease and 5, 10-methylenetetra hydrofolate reductase (MTHFR)'s C677T or folacin intakes, and to study the interaction of them in the occurring of congenital heart disease.

METHODSWe used case-control study (case = 104, control = 208) method. Cases and controls were chosen by age, sex and other conditions. The MTHFR C677T genotype distribution was analyzed by using polymerase chain reaction restricted fragment length polymorphism (PCR-RFLP), and non-conditional and multi-conditional logistic regression analysis were also used to analyze the correlationship and interaction of the factors.

RESULTSIn case group, the number of people in low folacin intake level was 38 (36.54%), which in control group was 21(10.10%). The intake level of folacin during pregnancy was related to congenital heart disease (chi(2) = 31.614, nu = 1, P < 0.0001). The value of OR was 1.417 with 95%CI 1.216 - 1.651, indicating that the low level of folacin intakes was a risk factor to the congenital heart disease. In case group, the number of TT genotype was 46 (44.24%), the number of CT genotype was 42 (40.38%), the number of CC genotype was 16 (15.38%). In control group, the number of TT genotype was 39 (18.75%), the number of CT genotype was 114 (54.81%), the number of CC genotype was 55 (26.44%). A significant genotype distribution difference was identified between case and control group (chi(2) = 23.13, nu = 2, P < 0.0001). Genotype MTHFR 677TT was a risk factor of congenital heart disease and the OR value was 3.437 (95%CI: 2.042 - 5.784). The interaction analysis suggested that the low level of folacin intakes and the MTHFR 677TT genotype had a positive adding effect in the occurring of congenital heart disease. After adjusted some factors such as the ages of parents, fetus age and sex, the effect values of interaction were 13.343 and 15.911 respectively, and the percentages of attributable interaction effects were 0.619 and 0.612. The percentages of effect values of interaction between pure factors were 0.649 and 0.637 and the population attributable risks were 25.26% and 27.82% according to the estimated exposure rate of population risk factors.

CONCLUSIONThe low level of folacin intakes during pregancy should be a risk factor to congenital heart disease and the MTHFR 677TT genotype be correlated to congenital heart disease. There is interaction between folacin intakes and the MTHFR 677TT genotype. Increasing the intakes of folacin among MTHFR 677TT genotype people might decrease the incidence rate of congenital heart disease.