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Updated: Jul 18, 2025

Quantitating Iron Transport Across the Mouse Placenta In Vivo Using Nonradioactive Iron Isotopes
Published on: May 10, 2022
Serum ferritin values in neonates <29 weeks' gestation are highly variable and do not correlate with reticulocyte
Timothy M Bahr1,2, Sylvia Tan3, Emily Smith3
1Division of Neonatology, Department of Pediatrics, University of Utah Health, Salt Lake City, UT, USA. tim.bahr@hsc.utah.edu.
Objectives:
To compare serum ferritin and RET-He values among extremely low gestational age neonates ELGANs with other markers of iron-deficient erythropoiesis.
Study Design:
This is a secondary analysis of the NICHD Darbepoetin Trial. Study data from placebo recipients who had a serum ferritin, a RET-He, and a mean corpuscular volume (MCV) measurement within a 24-hour period were analyzed for correlation.
Results:
Mixed linear regression models showed no association between ferritin and RET-He at both early (β = 0.0016, p = 0.40) and late (β = -0.0001, p = 0.96) time points. Positive associations were observed between RET-He and MCV at baseline, early, and late time points (p < 0.01, =0.01, <0.001, respectively), while ferritin was not associated with MCV at any time point.
Conclusions:
Our study shows that RET-He is better correlated with MCV as a marker of iron-limited erythropoiesis than ferritin. The results suggest that ferritin is limited as a marker of iron sufficiency in premature infants.
Study Identification:
FDA IND Number 100138; ClinicalTrials.gov number NCT03169881; NRN ID number NICHD-NRN-0058 (Darbe).

