Association between in vitro fertilization success rate and ambient air pollution: A possible explanation of within-year variation of in vitro fertilization success rate

Objective To evaluate patterns in air pollution concentrations and in vitro fertilization (IVF) success rates using data from a large, long-term clinical database. Methods We conducted a retrospective cohort study investigating South Korean women who pursued IVF and embryo transfer (IVF-ET) between 2011 and 2017. Hourly concentrations of air pollutants measured at 318 air quality monitoring sites in South Korea between 2011 and 2017 were obtained from the National Institute of Environmental Research. Monthly trends in pregnancy rates and concentrations of air pollutants were assessed. Results A total of 34,427 IVF-ET cycles in 18,478 patients were analyzed. The mean age of women at the time of IVF-ET was 36.6 years. The clinical pregnancy rate in the IVF-ET cycle was 30%. Analysis of pregnancy failure rates by month showed that IVF-ET failure rates tended to be higher in March and April and lower in July and August. Concentrations of air pollutants including particulate matter (PM) less than 10 μm in diameter, PM less than 2.5 μm in diameter, sulfur dioxide, nitrogen dioxide, and carbon monoxide were highest in March and April and lowest between July and September. Conclusion Within-year variations were similar between IVF-ET failure rates and air pollution concentrations based on analysis of a large, long-term database. Specifically, IVF-ET success rates were highest when PM concentrations were lowest. Further studies are warranted to examine the mechanisms accounting for the association between IVF success and air pollutant exposure.