Association between Ambient Air Pollution and Pregnancy Outcomes in Patients Undergoing In Vitro Fertilization in Chengdu, China: A retrospective study

Ambient air pollution has been a major concern in China due to its effect on population health. Exposure to ambient air pollution has negative impact on animal reproduction and fertility, however, its effect on human reproduction has been inconclusive. We conducted a retrospective study on in vitro fertilization (IVF) patients from Chengdu, Sichuan Province in western China, a city with persistent ambient air pollution. We analyzed the medical records of 1139 patients who underwent first conventional IVF cycles during 2014–2019. The relationship between six atmospheric pollutants (PM2.5, PM10, O3, NO2, SO2, CO) and IVF pregnancy outcomes were assessed by 1) stratification of maternal age into three groups (<35, 35–39, ≥40 years), and by 2) averaging pollutant concentration during different exposure windows. The results indicate that the association between ambient air pollution and IVF pregnancy outcomes (biochemical pregnancy and clinical pregnancy) is more significant for women in <35 years age group. Concentrations of PM2.5, PM10, NO2, SO2 and CO are negatively associated with the odds of biochemical pregnancy and clinical pregnancy, and concentration of CO in particular is associated with the largest reduction in odds. Conversely, O3 concentration is positively associated with biochemical pregnancy and clinical pregnancy. Moreover, pollutant concentration during long-term exposure window is associated with larger magnitude of change in the odds of biochemical pregnancy and clinical pregnancy. Findings from this study suggest that exposure to ambient air pollution during any period within the IVF treatment timeline would influence IVF pregnancy outcomes, and such influence is more pronounced in younger women (<35 years).