Individual-level air pollutants exposure and pregnancy outcomes in patients who underwent assisted reproductive technology: A retrospective longitudinal cohort study

Background: The effects of air pollution on the results of assisted reproductive technology (ART) treatment in terms of pregnancy outcomes were inconclusive. Methods We performed an individual-level retrospective longitudinal cohort study among 11,968 participants undergoing ART treatment from a general hospital in Hefei, China in 2013-20. Monthly mean concentrations of air pollutants [fine particulate matter (PM 2.5 ), suspended particulate matter (PM 10 ), ozone (O 3 ), sulfur dioxide (SO 2 ), Nitrogen dioxide (NO 2 ) and carbon oxide (CO)] during 3 Periods were obtained from ChinaHighAirPollutants (CHAP) dataset: respective Periods 1, 2 and 3 refer to 90 days, one or two years prior to oocyte retrieval. Multiple logistic regression model was applied to explore the impact of air pollution on four ART results (biochemical pregnancy, clinical pregnancy, pregnancy loss, and live birth). Results We observed negative relationships of PM 10 , PM 2.5 , CO and SO 2 exposures with pregnancy outcomes were more evident during one year exposure (Period 2). An interquartile range increment of ambient PM 10 , PM 2.5 , CO, and SO 2 exposures during Period 2 was associated with respective decrements of 5.85% (aOR: 0.94, 95% CI: 0.90–0.99), 7.82% (aOR: 0.92, 95% CI: 0.88–0.97), 10.60% (aOR: 0.89, 95% CI: 0.82–0.93) and 12.38% (aOR: 0.88, 95% CI: 0.82–0.93) on clinical pregnancy, while O 3 and NO 2 showed positive associations. Associations were stronger in patients undergoing frozen embryo transfer, aged < 32 years, with normal BMI, employed status, one embryo transferred, and in warm season. Conclusions Our data show that long-term individual-level exposure to the air pollutants of PM 10 , PM 2.5 , CO, SO 2 but not O 3 or NO 2 , especially in one year exposure before oocyte retrieval, could have a negative impact on ART outcomes.