Fetal blood ferritin and cobalamin in normal pregnancy

In a cross-sectional study of 75 singleton pregnancies at 16-38 weeks gestation serum cobalamin and ferritin concentrations were measured in fetal and maternal blood samples. Fetal serum cobalamin concentration did not change significantly with gestation but ferritin concentration increased. The median fetal serum concentrations of both ferritin and cobalamin were significantly higher than the respective values in the mother. The median fetal-maternal ratio for ferritin was 3.2 and for cobalamin 1.2. These findings demonstrate that from at least 16 weeks gestation, there is efficient iron storage in the fetus and transfer of cobalamin from the mother to the fetus against a concentration gradient.