Preterm birth is a major health concern in the United States and affects Black women at disproportionately high rates (Hoyert, 2025). Exposure to fine particulate matter (PM2.5), a harmful air pollutant, has been progressively acknowledged as a contributor to poor pregnancy outcomes (Jiao et al., 2024). This study examined whether PM2.5 exposure during pregnancy was associated with preterm birth among women living in nine metropolitan counties in Georgia between 2000 and 2002. Natality records were acquired from the National Vital Statistics System and matched with county-level Air Quality Index data. PM2.5 exposure was categorized as high or low using the median pregnancy AQI value of 64.5. Logistic regression models estimated odds ratios before and after adjustment for demographic and behavioral factors. Analyses were stratified by exposure level and race/ethnicity. In fully adjusted models, high PM2.5 exposure was associated with lower odds of preterm birth (OR = 0.906; 95% CI [0.868, 0.947]). Stratified analyses revealed a more complex pattern. Among births in the high exposure category, a higher mean pregnancy AQI was associated with increased preterm birth risk (OR = 1.013; 95% CI [1.002, 1.024]), while the opposite association was observed in the low exposure group (OR = 0.895; 95% CI [0.885, 0.905]). Race-stratified models showed a statistically significant association only among Non-Hispanic Black women (OR = 0.808; 95% CI [0.758, 0.861]), who were disproportionately represented in the high exposure category (20.85%). These findings highlight the complexity of PM2.5 exposure patterns and the importance of stratified analyses for understanding environmental contributions to preterm birth disparities.