Longitudinal evaluation of iron status during pregnancy: a prospective cohort study in a high-resource setting

Iron deficiency affects a large proportion of pregnant women worldwide, with potentially serious consequences for perinatal and infant outcomes, but well-powered, comprehensive analyses of longitudinal iron status during pregnancy are scarce.

This study aimed to evaluate the longitudinal changes in iron biomarkers across pregnancy and prevalence of iron deficiency in primiparous women in a high-resource setting and propose early pregnancy iron status cutoffs that predict iron deficiency in the third trimester.

In a prospective cohort of primiparous women with low-risk, singleton pregnancies in Ireland, iron [ferritin, soluble transferrin receptors (sTfR), total body iron (TBI)] and inflammatory markers (C-reactive protein, α-glycoprotein) were measured at 3 study visits: 15, 20, and 33 wk of gestation. Women with anemia (hemoglobin < 110g/L) at their first routine antenatal visit were excluded from this analysis.

Participants (N = 629) were Caucasian (98.2%) and born in Ireland (80.6%). The prevalence of iron deficiency (ferritin < 15 μg/L) increased throughout pregnancy, at 4.5%, 13.7% and 51.2% at 15, 20, and 33 wk of gestation, respectively. Using a ferritin threshold of <30 μg/L, rates of deficiency were 20.7%, 43.7%, and 83.8% across these time points, respectively. Application of sTfR of >4.4 mg/L generated similar prevalence data as ferritin of <15 μg/L at 7.2%, 12.6%, and 60.9%, respectively. Using TBI of <0 mg/kg, deficiency rates were lower than using ferritin or sTfR (P < 0.001). Using a cutpoint analysis method (area under the curve = 0.750), ferritin of <60 μg/L emerged as the ferritin threshold at 15 wk that predicted the presence of iron deficiency (ferritin < 15 μg/L) at 33 wk. Iron-containing supplements (mainly multivitamins) taken prepreganancy/early pregnancy was associated with reduced risk of deficiency throughout pregnancy, including the third trimester (odds ratio: 0.57; 95% confidence interval: 0.39, 0.82; P = 0.002).

Pregnancy places a remarkable strain on maternal iron status even in a high-resource, generally iron-supplemented population. Women should be screened early in pregnancy for iron status, with a suggested target ferritin concentration of >60 μg/L. This trial was registered at clinicaltrials.gov as NCT01891240 (IMPROvED Study; ==https://www.

gov/study/NCT01891240?cond=NCT01891240&rank=1).