The 677 C-T methylenetetrahydrofolate reductase mutation does not predict increased maternal homocysteine during pregnancy.

Objective: To test the hypothesis that, regardless of the presence of the 677 C-T methylenetetrahydrofolate reductase (MTHFR) mutation, maternal homocysteine concentrations will not be significantly different in women who are taking prenatal vitamins containing folic acid, and to test this relationship in preeclampsia because homocysteine concentrations are higher in preeclamptic pregnancies.

Methods: Fifty-seven pregnant white women (control and preeclamptic) with and without the 677 C-T MTHFR mutation were studied. Total plasma homocysteine and plasma folic acid were analyzed.

Results: Homocysteine concentrations were not different by MTHFR genotype (wild type 677 CC 8.7 +/- 5.6 microM versus mutant 677 TT 9.0 +/- 5.7 microM, P =.84) in preeclamptic or normal pregnancies. However, mean homocysteine concentrations were significantly increased in preeclamptic pregnancies compared with those in normal pregnancies (10.6 +/- 7.3 microM versus 7.2 +/- 3.0 microM, P <.03) as previously reported.

Conclusion: The 677 C-T MTHFR polymorphism does not significantly affect maternal homocysteine concentrations in most women taking prenatal vitamins including women with preeclampsia. The increase in plasma folic acid likely affects maternal homocysteine more than the MTHFR genotype. If homocysteine is considered a thrombophilia risk factor, the concentration of the amino acid and not a particular genotype should be determined.