Maternal Vitamin D Status, Oxidative Stress, and Implications for Neonatal Development: A Cross-Sectional Study

<b>Background</b>: Vitamin D (VD) plays a central role in calcium homeostasis during pregnancy and has been implicated in redox-related biological processes. While VD deficiency (VDD) has been consistently associated with adverse pregnancy outcomes, the relationships between VD insufficiency (VDI), maternal antioxidant-related biomarkers, and neonatal outcomes remain incompletely characterized, particularly during the third trimester. <b>Objective</b>: To determines the prevalence of VDI in third-trimester pregnant women and to examine its associations with antioxidant-related markers and selected neonatal outcomes. <b>Methods</b>: A cross-sectional study was conducted among pregnant women in the third trimester attending a tertiary referral hospital in Mexico City. Maternal serum 25-hydroxyvitamin D (25-OHD) concentrations were measured, along with a panel of redox-related markers, including 2,2-diphenyl-2-2picrylhydrazyl (DPPH) radical scavenging activity, reduced glutathione (GSH), glutathione S-transferase (GST), glutathione peroxidase (GPx), and oxygen radical absorbance capacity (ORAC). Neonatal anthropometric parameters were recorded at birth. Associations between maternal VD status, redox-related markers, environmental factors, and neonatal outcomes were evaluated using appropriate statistical analyses. <b>Results</b>: A high prevalence of VDI was observed in the study population. Maternal VDI was associated with lower activities of GSH, GST, and GPx. Passive exposure to tobacco smoke and season of sampling were also associated with lower VD concentrations. Neonates born to women with VDI had higher birth weight compared with those born to women with sufficient VD concentrations. Maternal serum 25-OHD concentrations correlated positively with selected antioxidant enzyme activities. <b>Conclusions</b>: In this cohort of third-trimester pregnant women, VDI co-occurred with environmental factors, differences in maternal redox-related markers, and selected neonatal outcomes. These findings support an associative framework in which suboptimal VD status during the third trimester is accompanied by variations in redox-related markers. Longitudinal and mechanistic studies are needed to clarify the temporal sequence and biological relevance of these associations.