Early-pregnancy serum iron as a nutrition-related clinical laboratory indicator for preeclampsia risk stratification: a retrospective cohort study.

Background: Nutrition-related clinical laboratory indicators are valuable for risk assessment, early identification, and precision management in obstetric and gynecologic diseases. Serum iron, a commonly used laboratory marker reflecting iron metabolism status, has shown inconsistent associations with preeclampsia (PE). Objective: To investigate the association between early-pregnancy serum iron levels and the risk of PE, and to evaluate their associations with low birth weight, cesarean delivery, and preterm birth. Methods: This single-center retrospective cohort study included 37,643 pregnant women. Early-pregnancy serum iron level was the exposure variable, PE the primary outcome, and low birth weight, cesarean delivery, and preterm birth secondary outcomes. Logistic regression models (non-adjusted, Adjust I, and Adjust II) assessed associations between serum iron and each outcome. Smooth curve fitting illustrated the relationship between serum iron and PE risk. Stratified analyses by age, BMI, and parity, along with interaction analysis, evaluated the robustness of the association. Results: Serum iron levels were lower in the PE group than in the non-PE group (20.45 ± 6.16 vs. 21.32 ± 6.11 μmol/L, Conclusion: Higher early-pregnancy serum iron levels were significantly associated with lower risk of PE, although its clinical utility still requires further validation in prospective studies.