Window-specific effects of ultraviolet radiation and air pollution on ovarian reserve in infertile women: A retrospective cohort study

The environmental factors affecting ovarian reserve are not fully understood, particularly during vulnerable stages of follicular development. In this retrospective cohort study of 2804 infertile women, we assessed the associations of ambient ultraviolet radiation (UV) and air pollutants with ovarian reserve markers. Serum levels of anti-Müllerian hormone (AMH) and follicle-stimulating hormone (FSH) were measured, and residential exposures to UV radiation, nitrogen dioxide (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO), ozone (O₃), and fine particulate matter (PM₂.₅, ≤2.5 μm) were assigned based on participants' residential addresses. UV exposure was estimated using satellite-derived erythemal daily dose data, whereas air pollutant exposures were derived from monitoring-station data and ordinary-kriging surfaces. We focused on five exposure windows spanning approximately 2 to 12 months before hormone assessment, corresponding to key stages of folliculogenesis. Multivariable linear and logistic regression models were used, adjusting for demographic, lifestyle, and reproductive factors. Higher UV exposure during the earliest window was associated with lower odds of diminished ovarian reserve (AMH ≤1.1 ng/mL; odds ratio 0.73, 95% CI: 0.56-0.94), whereas positive associations during intermediate windows were less consistent across adjustment models. Interquartile-range increases in NO₂ and CO were associated with reductions in AMH of 7.20% to 10.12% during early and middle stages. CO was associated with increases in FSH across all windows (7.71% to 9.81%), and PM₂.₅ was associated with higher FSH during late follicular development. Joint exposure analyses suggested that higher NO₂ and SO₂ concentrations may modify UV-associated changes in FSH and AMH, with more pronounced associations observed among women aged <35 years and those with BMI ≥24 kg/m². These findings suggest stage-specific associations of UV radiation and air pollution with ovarian reserve, particularly during early and late follicular development, but require validation in prospective and multi-center studies.