Association Between Folic Acid Use and Serum One-Carbon Metabolism-Related Metabolites in Maternal and Cord Blood of Japanese Pregnant Women

Background/Objectives: Folic acid (FA) intake impacts one-carbon metabolism (OCM), which is crucial for fetal development and epigenetic regulation. While FA supplementation is known to lower homocysteine levels, its comprehensive effects on OCM-related metabolites in maternal and cord blood remain unclear. This study aimed to investigate the association between FA use and serum OCM-related metabolite profiles in Japanese pregnant women. Methods: We analyzed 146 mother-infant pairs from the Chiba study of Mother and Child Health (C-MACH) cohort. Blood samples were collected in early pregnancy, late pregnancy, and at delivery (maternal and cord blood). FA use was assessed via self-administered questionnaires. Serum concentrations of 18 OCM-related metabolites, including 5-methyltetrahydrofolate (5-MTHF) and homocysteine, were measured using LC-MS/MS. Results: FA users exhibited significantly higher 5-MTHF and lower total homocysteine concentrations in maternal blood at all time points and in cord blood compared to non-users. Compared to non-users, FA users exhibited a lower serine/glycine ratio in early pregnancy, a higher betaine/DMG ratio in maternal blood at delivery, and higher S-adenosylmethionine and total cysteine concentrations in maternal blood during late pregnancy. In cord blood, unmetabolized folic acid concentrations did not differ significantly between FA users and non-users. Furthermore, the cord-to-maternal 5-MTHF ratio was significantly lower in FA users. Conclusions: Our findings suggest that FA use during pregnancy may contribute to the optimization of OCM in both the mother and fetus.