• Endothelial nitric oxide synthase;
  • homocysteine;
  • metylenetetrahydrofolate reductase;
  • nitric oxide;
  • polymorphism;
  • recurrent pregnancy loss

Problem:  It is controversial whether polymorphisms of methylenetetrahydrofolate reductase (MTHFR) and the endothelial nitric oxide synthase (eNOS) are associated with recurrent pregnancy loss.

Method of study:  We studied the frequency of the C677T polymorphism of MTHFR and a eNOS gene polymorphism, as well as the plasma levels of homocysteine and NO, in 85 cases with a history of two or more unexplained embryonal losses, 40 patients suffering fetal loss and 76 controls.

Results:  The frequency of the MTHFR gene T allele, which has been reported to be associated with miscarriages, in patients suffering fetal loss was rather significantly lower than in controls whereas there was no difference in the frequency of the eNOS gene A allele. There were no differences in the plasma homocysteine levels among the three groups. However, the NO concentrations in the embryonal loss and fetal loss groups were significantly higher than that in controls.

Conclusion:  We conclude that the NO concentration but not the polymorphism of MTHFR and eNOS gene and hyperhomocysteinemia are associated with recurrent pregnancy loss in Japanese.