Functional iron deficiency markers are absent during pregnancy despite evidence of low iron stores

Abstract

Introduction Functional iron deficiency parameters predict iron-restricted erythropoiesis more precisely than ferritin. Ferritin and erythropoiesis can be affected by inflammation and hormonal alterations. We hypothesize that the association between low ferritin concentrations and iron-restricted erythropoiesis is not comparable between pregnant and non-pregnant women. Materials and methods Pregnant women ( n = 926) were included at week 12 of gestation. Ferritin concentrations, %hypochromic erythrocytes (%HYPO), %microcytic erythrocytes (%MICRO), reticulocyte haemoglobin content (MCHr), mean cell volume (MCV) and mean cell haemoglobin (MCH) were analysed. Data were compared with non-pregnant women ( n = 1302). Results Functional iron deficiency parameters (%HYPO, %MICRO, MCHr) were present in, respectively, 3.9%, 14.3% and 2.3% off all pregnant women. Univariate analysis of low ferritin (<20 μg/L) showed significant differences between non-pregnant versus pregnant women; %HYPO (10.92% vs. 0.92%), increased %MICRO (4.33% vs. 1.00%) and decreased MCHr (24.9 pg vs. 29.5 pg), respectively. In the logistic regression analysis, MCHr, %MICRO and MCV were independently associated with low ferritin concentrations in pregnant women, while %HYPO and %MICRO were independently associated variables in non-pregnant women with low ferritin concentrations. Discussion Functional iron deficiency is significantly less frequent in pregnant women compared with iron-deficient non-pregnant women. During pregnancy, iron metabolism might be differentially regulated for optimal fetal growth and development despite low maternal iron stores.