The concentration of active folic acid in the fetal blood is higher than that of the mother due to active placental transport. The average concentration is highest in the umbilical cord. On the other hand, there are no maternal-fetal differences in plasma levels of folic acid or inactive metabolites, supporting the evidence that active placental transfer of these substances does not occur. Thus, it is clear that supplementation with folic acid, unlike active folate, cannot reach adequate concentrations in the fetus for healthy growth.
Active folate, folate and folic acid in maternal and umbilical cord blood: concentration of different forms of folate in maternal serum and in the corresponding umbilical cord serum. Active Folic Acid (5-MTHF) supplementation during pregnancy is a valid source of folate for the fetus.
