Longitudinal Assessment of Oxidative Stress Biomarkers During Physiological Pregnancy and Their Relevance for...

Background/Objectives: Pregnancy is characterized by profound metabolic and physiological adaptations that influence systemic redox balance. Longitudinal data assessing trimester-specific changes in antioxidant status and oxidative stress markers remain limited. Methods: In this longitudinal study, plasma levels of non-enzymatic antioxidants (vitamins A, C, E, and carotenoids) and oxidative stress markers (malondialdehyde, conjugated dienes, protein carbonyls, and DNA strand breaks) were analyzed in 31 healthy non-smoking pregnant women during the first, second, and third trimester. Environmental tobacco smoke exposure was evaluated using urinary cotinine. Statistical analyses were performed using Friedman repeated-measures tests followed by Dunn's post hoc comparisons with Benjamini-Hochberg false discovery rate correction. Results: Vitamin A was the only antioxidant that consistently decreased across all trimesters and represented the only antioxidant marker showing a consistent decline. In contrast, α-tocopherol, γ-tocopherol, xanthophylls, and lycopene increased significantly during gestation, whereas vitamin C remained relatively stable. Markers of oxidative damage, including malondialdehyde, conjugated dienes, protein carbonyls, and DNA strand breaks, showed significant trimester-dependent increases. Total antioxidant capacity (FRAP) remained unchanged throughout pregnancy. Conclusions: Physiological pregnancy is characterized by coordinated, marker-specific adaptations in systemic redox balance. Vitamin A was the only antioxidant showing a consistent decline across gestation, whereas several lipid-soluble antioxidants increased and total antioxidant capacity remained stable. These findings indicate that pregnancy is associated with increased oxidative activity accompanied by preservation of systemic antioxidant capacity rather than global antioxidant depletion.