Effects of Iron Supplementation on Red Blood Cell Hemoglobin Content in Pregnancy

Although a mild degree of anemia is common in the third trimester of pregnancy, it remains a challenge to establish whether a decrease in hemoglobin (Hb) concentration is physiological or pathological. The World Health Organization suggested a Hb concentration of 110 g/L to discriminate anemia. Several European investigators recommended Hb cut-off values of between 101–110 g/L. The aim of this study was to establish short-term effects of iron supplementation on the hemoglobin content of reticulocytes (Ret-He) and red blood cells (RBC-He) in case of suspected iron deficient erythropoiesis (IDE) in the third trimester of pregnancy. Twenty-five subjects with suspected IDE during pregnancy (Hb ≤ 110g/L, Ret-He < 29.6 pg, zinc protoporphyrin > 75 mol/mol hem) participated in the study. After iron supplementation, reticulocyte counts increased from 0.061 ± 0.015 x 10¹²/L to 0.079 ± 0.026 x 10¹²/L and Ret-He increased from 23.6 ± 2.8 pg to 28.3 ± 2.6 pg (P ≤ 0.001). RBC-He increased from 26.9 ± 1.9 pg to 27.4 ± 1.8 pg (not significant, NS) and Ret-He/RBC-He ratio increased from 0.97 ± 0.06 towards 1.07 ± 0.05 (P ≤ 0.001). Hb concentrations demonstrated an obvious increase from 105 ± 6 g/L towards 115 ± 5 g/L (P ≤ 0.001) after supplementation. An obvious increase in RBC distribution width was observed from 45.0 ± 3.6 fL towards 52.3 ± 7.0 fL (P ≤ 0.001). We recommend that Ret-He and Ret-He/RBC-He ratio be integrated into the protocols for anemia screening and for monitoring effects of iron supplementation during pregnancy. In particular, the parameters should be considered in subjects with Hb results in the controversial range of 101–108 g/L.