Investigation of the association between maternal serum ferritin levels and preterm delivery: A systematic review and meta-analyses

BACKGROUND: Preterm delivery (PTD) has been a significant cause of neonatal morbidity and mortality. Maternal serum ferritin, a biomarker of both iron stores and systemic inflammation, has shown inconsistent associations with PTD risk in individual studies. OBJECTIVE: This systematic review and meta-analysis aimed to clarify the relationship between maternal serum ferritin levels and the risk of PTD. METHODS: Following the PRISMA guidelines, we searched PubMed, Scopus, Web of Science, and Google Scholar up to August 2025. Twenty-four observational studies with more than 10000 participants were included. Pooled standardized mean differences (SMDs) and odds ratios (ORs) were calculated using random-effects models. The ROBINS-1 tool was used to assess the quality of the studies and the risk of bias. RESULTS: = 97.3%), with the strongest association observed in the second trimester (SMD 1.18, 95% CI 0.74-1.63). No independent predictive role for ferritin was shown (random-effects OR 1.05, 95% CI 0.97-1.13). High heterogeneity and evidence of publication bias were noted. Hemoglobin levels did not differ between groups. CONCLUSION: Elevated levels of maternal serum ferritin, especially during the second trimester, are linked to PTD. However, the adjusted OR estimates have not shown statistical significance. There is considerable variability among the studies and a risk of bias that warrants cautious interpretation. Additionally, the diagnostic thresholds reported differ greatly and lack sufficient validation for clinical application. It is essential to conduct standardized prospective studies before ferritin-based clinical decision-making can be endorsed.