We evaluated the effect of iron supplementation on biochemical indicators of iron status, namely hemoglobin (Hb), serum ferritin (SF), and serum transferrin receptor (sTfR), during pregnancy.
A prospective study was conducted in 73 pregnant women who received daily supplements of 60 mg of iron and 500 microg of folic acid for 100 d from 19 wk of gestation. The indicators of iron status (Hb, SF, and sTfR) at 19, 27, and 35 wk of gestation were analyzed. The response of iron status indicators to iron supplementation was assessed in the cohort and in pregnant women who were anemic (n = 35) and non-anemic (n = 38) at 19 wk.
All three indicators of iron status during supplementation (27 and 35 wk) were similar to the presupplementation status. The sTfR as an indicator correlated negatively with presupplementation Hb levels (r = -0.417). Based on sTfR level in iron-adequate pregnant women, a cutoff value of at least 12.0 mg/L was derived to define iron deficiency in pregnancy. When the response was tested in anemic pregnant women, iron supplementation improved mean Hb (P < 0.05) at the end of 35 wk (96 +/- 8.8 to 110 +/- 20.2 g/L) of gestation, with no change in SF. Conversely, non-anemic pregnant women showed a significant increase in SF and a decrease in Hb (122 +/- 11.6 to 112 +/- 15.2 g/L) at 35 wk of gestation. A significant effect of iron intake on sTfR was seen only among iron-deficient anemic women.
These observations suggest that, during pregnancy, sTfR responds to iron supplementation when there is iron-deficiency anemia and therefore can be used as an indicator.