Exposure to ambient air pollution and outcomes in women undergoing in vitro fertilization

BACKGROUND

This study estimates the effect of exposure to air pollution prior to the start of in vitro fertilization (IVF) on fertilization, embryo quality, pregnancy, and live birth. We expand upon previous research by estimating exposure using differing exposure time windows, examining the role of infertility, and examining potential mechanistic pathways.

METHODS

This retrospective cohort study evaluated women undergoing their first autologous IVF cycle. Clinical and demographic data were extracted from medical records. Air pollution exposures at residential address prior to IVF start were predicted for fine particulate matter (PM2.5), course PM (PM10), nitrogen dioxide (NO2), and oxides of nitrogen (NOX) using spatial and spatiotemporal modeling. Distance to roadway was evaluated as an alternate exposure measure. Effect modification by infertility was assessed on an additive scale using relative excess risk due to interaction (RERI). Lastly, a mediation analysis was conducting evaluating anti-Müllerian hormone (AMH) as a mediator in the association between near roadway residence and pregnancy.

RESULTS

The pollutant exposure analysis suggest weak associations between long-term exposure and IVF outcomes, specifically NO2 on percent oocytes fertilized, live birth, and pregnancy loss as well as PM2.5 on live birth and pregnancy loss; however, we cannot estimate these effects with any certainty. Near roadway residence was associated with a lower likelihood of pregnancy. Effect modification analysis suggested that there may be synergistic effects between high exposure to PM2.5, PM10, and NO2 and a diagnosis of diminished ovarian reserve or male infertility on the likelihood of a live birth. Lastly, AMH, a marker of ovarian reserve, was not a mediator between near roadway residence and likelihood of pregnancy in this study population.

CONCLUSIONS

This study suggests an association between exposure to air pollution and IVF outcomes, specifically pregnancy. Further research in this area may focus on pregnancy as an early outcome of interest rather than live birth. This study also suggests that diminished ovarian reserve and male factor infertility in addition to air pollution may have synergistic effects. Focusing future research on these infertility types may better inform potential subgroups where interventions on air pollution exposure may have the most impact.