Background <p>A substantial body of empirical evidence suggests that dietary antioxidants may play a critical role in promoting positive pregnancy outcomes. However, despite the well-documented benefits of individual antioxidants in reducing oxidative stress and associated complications, research investigating the association between overall antioxidant intake—quantified through the composite dietary antioxidant index (CDAI)—and pregnancy health remains scarce. This research fills a critical void by performing a cross-sectional evaluation based on data collected from the National Health and Nutrition Examination Survey (NHANES) covering the years 2007 to 2018. Through an in-depth assessment of the correlation between CDAI and maternal health outcomes, this study aims to offer fresh perspectives on the possible advantages of a well-rounded antioxidant intake throughout pregnancy.</p> Methods <p>A weighted multiple logistic regression analysis was utilized to examine the relationship between CDAI and pregnancy outcomes, controlling for potential confounders. To further explore heterogeneity within the data, subgroup analyses were performed to identify population-specific variations in the observed associations. Additionally, non-linear trends were assessed using smoothing curve fitting techniques, allowing for a more comprehensive examination of potential complex relationships. To pinpoint threshold effects within the dataset, a segmented weighted linear regression model was employed, facilitating the identification of an inflection point where the nature or magnitude of the association may shift. This multi-faceted analytical approach ensures a robust evaluation of the impact of dietary antioxidant intake on pregnancy-related health outcomes.</p> Results <p>The multivariate logistic regression analysis revealed that higher levels of CDAI were significantly associated with an increased risk of infertility, after adjusting for various potential confounders. Specifically, individuals in the third quartile of CDAI (Q3) exhibited a 2.04-fold increase in the odds of infertility compared to those in the first quartile (OR 2.035, 95% CI 1.243–3.331, <i>p</i> = 0.00471), while those in the fourth quartile (Q4) faced a 3.58-fold greater risk (OR 3.581, 95% CI 2.249-5.700, <i>p</i> &lt; 0.00001). These associations remained significant across subgroups differentiated by age, body mass index (BMI), educational attainment, and family income-to-poverty ratios.Additionally, when CDAI was treated as a continuous variable, a 0.1 unit increase was found to be associated with a more than 7% increase in the odds of achieving pregnancy (OR 1.076, 95% CI 1.042–1.110, <i>p</i> &lt; 0.00001). This relationship highlights the potential impact of antioxidant consumption on reproductive health, indicating that higher antioxidant intake may enhance fertility outcomes. These findings warrant further investigation into the mechanisms by which antioxidants influence fertility, as well as potential public health recommendations for dietary interventions aimed at improving reproductive health.</p> Conclusions <p>This study elucidated a non-linear association between CDAI and pregnancy outcomes within a comprehensive, nationally representative cohort. The observed relationship suggests that the impact of antioxidant intake on reproductive health may vary at different levels of CDAI, indicating the presence of potential threshold effects. These findings highlight the intricate role of dietary antioxidants in pregnancy health and underscore the importance of further research to refine dietary guidelines aimed at optimizing reproductive outcomes.</p>