Serum ferritin as an assessment of iron stores and other hematologic parameters during pregnancy.

Serum ferritin concentration has been thought to be a useful index of the status of iron stores. Serum ferritin concentration and hemoglobin, serum iron, and transferrin levels were measured simultaneously. In first-trimester pregnant women, serum iron and ferritin levels increased significantly as compared with those in nonpregnant women. During the second and third trimesters, serum iron and ferritin levels decreased significantly. However, hemoglobin levels showed little change and transferrin levels increased. At delivery, serum iron levels in cord blood were about twice as high as those in maternal blood, and serum ferritin levels in cord blood were about 10 times higher than those in maternal blood. Serum iron and ferritin levels between maternal and cord blood were well correlated. These results suggest that maternal body iron storage is depleted during the second trimester in patients who are not receiving supplemental iron. The data are also consistent with the concept that maternal serum iron is transported across the placenta by active transport and that a deficiency of maternal iron storage results in a deficiency of neonatal iron storage.