Effect of iron supplementation on serum ferritin levels during and after pregnancy.

Serum ferritin, total plasma ferritin and haematological indices were determined during and for 6 months after normal pregnancy in 45 healthy women, 21 of whom took oral iron supplements. The physiological effect of pregnancy was to markedly depress serum ferritin concentration. During unsupplemented pregnancy median serum ferritin concentration decreased to approx. 6.0 micrograms/l by 28 weeks gestation, this concentration was maintained until term and was associated with the appearance of erythrocyte microcytosis during the third trimester. At 6 months postpartum, individual and average serum and total plasma ferritin values showed a deficit compared with the values recorded at the beginning of pregnancy. Oral iron supplementation during pregnancy modified the fall in serum ferritin, median serum ferritin concentrations remained about 14.0 micrograms/l after 28 weeks gestation; normocytic erythropoiesis was maintained throughout the third trimester and no deficit in serum and total plasma ferritin occurred as a result of pregnancy. It is concluded that routine oral iron administration should be recommended during pregnancy, certainly after 28 weeks gestation.