Markers of iron status are associated with stage of pregnancy and acute-phase response, but not with parity among pregnant women in Guinea-Bissau

Abstract

While prenatal Fe supplementation prevents maternal Fe deficiency and anaemia, it is uncertain whether it improves infant health outcomes, at least when taken by Fe-replete women. Inflammation as well as physiological changes complicates the assessment of Fe status during pregnancy. In the present study, we measured the concentrations of serum ferritin and soluble transferrin receptors (sTfR), Hb and the acute-phase proteins C-reactive protein (CRP) and α1-antichymotrypsin (ACT) in a cross-sectional study among 738 pregnant women attending antenatal care in Guinea-Bissau, West Africa. Multiple linear regression analysis was used to identify the predictors of Fe status markers. The mean gestational age was 23 (sd7) weeks. Serum ferritin values were lower with progressing gestation, from 27 % lower during weeks 16–20 of gestation up to 59 % lower after 29 weeks of gestation compared with early pregnancy. Using cut-off values for Fe deficiency as established in non-pregnant individuals, 52 % of the women had sTfR levels >2·3 mg/l, while only 25 % had serum ferritin levels < 12 μg/l. Serum ferritin but also sTfR levels were elevated at increased serum CRP and ACT levels. The proportion of sTfR >2·3 mg/l decreased to 47 % after adjustment for elevated serum CRP and ACT levels. On the contrary, the proportion of serum ferritin < 12 μg/l increased to 33 % after adjustment for ACT and CRP. The high proportion of elevated serum sTfR calls for pregnancy-specific cut-offs since increased erythropoiesis is expected in response to increased plasma volume of pregnancy. The present study further underlines the need to adjust for inflammation when serum sTfR and serum ferritin are used to assess Fe status in pregnancy.