Association between PM2.5 components and poor ovarian response in assisted reproductive technology patients: A retrospective cohort study identifying sensitive exposure windows in China

Environmental factors, particularly various components of fine particulate matter (PM_2.5) (i.e., sulfate [SO₄^2-], nitrate [NO₃^-], ammonium [NH₄⁺], organic matter [OM] and black carbon [BC]), are increasingly recognized as potential risk factors for poor ovarian response (POR) in fertility treatments. However, existing research is limited, and the critical periods of vulnerability to exposure to PM_2.5 and its components remain unclear. In this retrospective cohort study, we included 38,619 patients undergoing their first in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatment, defining POR as the primary outcome based on the POSEIDON criteria. We divided the six months prior to oocyte pick up (OPU) into different exposure windows and used logistic regression models to assess the association between pollutants and POR. Results showed that exposure to PM_2.5 and its components in the three months before OPU significantly increased the odds of POR. The distributed lag nonlinear model (DLNM) analysis revealed the lagged effects of PM_2.5 component exposure, particularly during lag weeks 2-5, where exposure was significantly associated with the occurrence of POR. This period may represent a sensitive window for exposure. Meanwhile, the restricted cubic spline (RCS) analysis indicated that the odds of POR gradually increased with higher pollutant concentrations. These findings underscore the urgent need for public health measures during sensitive stages of follicular development, particularly policies aimed at reducing environmental pollutant exposure among women of reproductive age to protect reproductive health.