Change of Erythropoiesis and Serum Transferrin Receptor Levels with Gestational Age in Healthy Pregnant Women

Choi, Jong Weon; Im, Moon Whan; Pai, Soo Hwan

Abstract

BACKGROUND: To investigate the change of iron dynamics, erythropoiesis, and serum transferrin receptor (sTfR) concentration during pregnancy, we measured the reticulocyte subpopulations, reticulocyte maturity index (RMI) and sTfR concentration in normal pregnant women. Also we determined which parameter among sTfR, serum iron, or serum ferritin is more representative for clinical features and erythropoiesis in pregnant women. Method: A total of 283 pregnants were examined for reticulocyte subpopulations, sTfR, and a battery of iron parameters. Reticulocytes and their subpopulations were automatically analyzed by flow cytometry (R-3000; Sysmex, Toa, Japan). Serum iron and TIBC were assayed with the automatic chemical analyzer (Hitachi 747; Hitachi, Tokyo, Japan) and serum ferritin was measured by the chemiluminescence method (ACS 180; Chiron, USA). Soluble transferrin receptor was measured by the immunoenzymometric method (ELISA ; Orion Diagnostica, Finland).
RESULTS
There was no significant difference in sTfR concentration between pregnant women in the 1st trimester (2.29+/-0.45 mg/L) and non-pregnant women (2.18+/-0.46 mg/L). However, the sTfR concentration gradually increased with gestational age from the 2nd trimester of pregnancy and reached maximal concentration (5.76+/-1.12 mg/L) in the 3rd trimester. The mean sTfR in postpartum 12 weeks was similar to that in the 1st trimester. RMI in the 3rd trimester was three- to four- fold higher than that in the 1st trimester. The sTfR correlated better with RMI (r=0.62, P<0.01), MCH (r=-0.61, P<0.01) and gestational age (r=0.51, P<0.01) than to serum iron and ferritin.
CONCLUSIONS
The sTfR concentration increases with gestational age during pregnancy and returns to normal at 12 weeks after delivery. Elevated sTfR concentration during pregnancy seems to be more influenced by erythroid TfR turnover than by iron depletion. The sTfR is a more reliable predictor of erythropoiesis and iron status during pregnancy than serum iron or ferritin.