Poor air quality index on the day of embryo transfer may decrease the rate of embryo transfer success

Area of Science:

• Reproductive Medicine
• Environmental Health
• Epidemiology

Background:

• Wildfire smoke in Eastern Canada caused significant air pollution in New York during June-July 2023.
• Air quality index (AQI) levels varied, creating distinct exposure groups for patients undergoing fertility treatments.

Purpose of the Study:

• To investigate the association between the air quality index (AQI) on the day of embryo transfer (ET) and clinical pregnancy rates (CPR).
• To analyze the impact of varying AQI levels on secondary fertility outcomes, including live birth rates.

Main Methods:

• Retrospective cohort study of 190 fresh or frozen embryo transfers (ETs) at a single academic fertility center.
• Patients were stratified into three groups based on EPA-defined AQI categories: Good (0-50), Moderate (51-100), and Unhealthy (>100).
• Chi-square analyses compared clinical pregnancy rates (CPR) and other outcomes between AQI groups, including a separate analysis for 127 single euploid embryo transfers (SETs).

Main Results:

• Clinical pregnancy rates (CPR) were significantly lower for ETs performed on days with Unhealthy AQI (27.3%) compared to Good (62.0%, p=0.02) and Moderate (64.9%, p=0.03) AQI days.
• For single euploid embryo transfers (SETs), CPR was lower on Unhealthy AQI days (37.5%) compared to Good AQI days (70.8%), though not statistically significant (p=0.052).
• Live birth rates (LBR) were also lower on Unhealthy AQI days, but did not reach statistical significance.

Conclusions:

• Poor air quality, specifically an Unhealthy AQI on the day of embryo transfer, is associated with a reduced clinical pregnancy rate (CPR).
• These findings suggest that environmental air quality may impact fertility treatment outcomes, warranting further investigation into protective measures.