Purpose <p>To examine whether exposure to air pollution around the fresh embryo transfer affects the dynamic progression from infertile state to biochemical pregnancy, clinical pregnancy, and ultimately to live birth.</p> Methods <p>We included 12,453 infertile women who underwent fresh embryo transfer at a major assisted reproduction specialist hospital in Chengdu, China, between 2019 and 2022. We conducted multistate modeling to explore the association between six air pollutants PM_2.5, PM₁₀, O₃, NO₂, SO₂, and CO and three key transitions.</p> Results <p>Among women with a clinical pregnancy, 5601 (85.51%, 5601/6550) achieved a birth. We observed that exposure to higher concentrations of PM_2.5, PM₁₀, and O₃ in the 3&#xa0;months prior to embryo transfer was negatively associated with the probability of successful progression of the three outcomes. For each 10&#xa0;μg/m³ increase in PM_2.5, the hazard ratios (HRs) were 0.905 (95% CI, 0.899, 0.910) for transition from infertility to biochemical pregnancy, 0.919 (0.915, 0.923) for biochemical pregnancy to clinical pregnancy, and 0.992 (0.984, 0.999) for clinical pregnancy to live birth. Mediation analysis indicated that the number of high-quality embryos at the cleavage stage accounted for 10%, 5.27%, and 3.79% of the association between PM_2.5, PM₁₀, and O₃ and live birth, respectively.</p> Conclusion <p>This study provides the novel evidence that exposure to PM_2.5, PM₁₀, and O₃ during the 3&#xa0;months prior to embryo transfer may play an important role in the progression of assisted reproductive outcomes in infertile patients, particularly in the early stage. In addition, the number of high-quality embryos at the cleavage stage may act as potential mediators.</p>