A comparative study of maternal and umbilical cord iron indices in term infants born after fetal growth restriction and appropriate-for-gestational-age infants

Abstract

Fetal growth restriction (FGR) may compromise fetal iron accretion through placental dysfunction and increased erythropoietic demand. This study compared maternal and umbilical cord iron indices between term infants born after FGR and appropriate-for-gestational-age (AGA) infants. This prospective hospital-based cross-sectional analytical study enrolled 100 mother-infant pairs (50 FGR and 50 AGA) at a tertiary center in southeastern Iran during the 24-month period from January 2024 through December 2025. FGR was operationally defined as birth weight below the 10th percentile plus at least one antenatal indicator of pathological growth restriction or placental dysfunction. Maternal and cord blood were analyzed for hemoglobin, ferritin, serum iron, total iron-binding capacity (TIBC), transferrin saturation, and complete blood count parameters. Analyses included group comparisons, correlations, analysis of covariance, and multivariable linear regression. Maternal hemoglobin and ferritin did not differ significantly between groups. Mean cord ferritin was lower in the FGR group than in the AGA group (78.4 ± 22.5 vs. 142.6 ± 35.8 µg/L; mean difference − 64.2 µg/L, 95% CI − 76.2 to − 52.2; p < 0.001). FGR infants also had higher hemoglobin and red cell distribution width, lower serum iron, higher TIBC, and lower transferrin saturation. Low cord ferritin (< 76 µg/L) occurred in 52% of FGR infants and 8% of AGA infants (absolute risk difference 44% points, 95% CI 26.7 to 58.1; p < 0.001). Maternal-cord ferritin correlation was weaker in the FGR group ( r = 0.33, 95% CI 0.06 to 0.56; p = 0.018) than in the AGA group ( r = 0.77, 95% CI 0.63 to 0.86; p < 0.001). After adjustment for gestational age, the between-group difference in cord ferritin remained substantial (adjusted mean difference − 61.8 µg/L, 95% CI − 73.5 to − 50.1; p < 0.001). Term infants born after FGR had lower cord ferritin and a biochemical pattern consistent with reduced iron stores and iron availability at birth despite similar maternal iron indices. These findings support further evaluation of risk-based postnatal iron monitoring, but they do not establish postnatal iron deficiency, neurodevelopmental impairment, or the benefit of routine iron supplementation.