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Abstract

Background: Preterm birth remains a leading cause of neonatal morbidity and mortality worldwide, with significant implications for long-term child health. Among the various maternal risk factors, vitamin D deficiency has gained attention for its potential role in adverse pregnancy outcomes, including preterm delivery. However, the current literature presents inconsistent findings, necessitating a comprehensive evaluation of existing evidence to clarify this association.
Objective: This systematic review aims to assess the relationship between maternal vitamin D deficiency during pregnancy and the risk of preterm birth.
Methods: A systematic review was conducted following PRISMA guidelines. Databases including PubMed, Scopus, Web of Science, and the Cochrane Library were searched for studies published between 2019 and 2024. Inclusion criteria encompassed observational studies and randomized controlled trials examining maternal 25(OH)D levels and preterm birth outcomes. Studies involving animals, non-English publications, and lacking full-text access were excluded. Two independent reviewers conducted screening, data extraction, and quality assessment using the Newcastle-Ottawa Scale and Cochrane Risk of Bias Tool.
Results: Eight studies involving 15,392 pregnant women were included, comprising five cohort and three case-control studies. All studies reported a statistically significant association between maternal vitamin D deficiency (commonly defined as <20 ng/mL) and increased risk of preterm birth. Adjusted odds ratios and risk ratios across studies indicated a consistent trend, with p-values ranging from <0.05 to <0.001. Risk of bias was generally low to moderate.
Conclusion: Maternal vitamin D deficiency is significantly associated with an elevated risk of preterm birth. These findings support the clinical relevance of monitoring and managing vitamin D levels during pregnancy. Nonetheless, further large-scale randomized trials are needed to confirm causality and define optimal intervention strategies.