Association between short-term exposure to particulate matter air pollution and outcomes of assisted reproduction technology in Lombardy, Italy: a retrospective cohort study

The harmful effect of polluted air on spontaneous fertility has been consistently reported. However, the specific pollutants involved in determining this effect are still to be clarified. The study of Assisted Reproductive Technology (ART) populations is particularly helpful in this context since it allows to monitor the key events of the reproductive process. We analyzed the medical records of 2122 patients who underwent fresh or frozen ART cycles during 2014-2017 in the Lombardy region, north-west Italy. Each subject was assigned the daily PM10 estimates concentration, at the municipality of residence, during the induction of multiple follicular growth. A multivariable linear regression model with a repeated-measures design was used to estimate the association between short-term exposure to PM10 and ART outcomes, A reduction in the number of retrieved oocytes in association with 10 μg/m3 increment of the pollutant estimated at 13-14 days before oocyte retrieval (Day 0) and a decrease in the percentage of metaphase II oocytes for 1-week and 2-weeks mean exposure before day 0 were observed. For cumulative pregnancies, a significant lag time change effect for PM10 exposure (Day -9-0) has been detected, by means of multivariable logistic regression models. An increase in PM10 exposure was associated with a decrease in clinical and ongoing pregnancies while a decrease in PM10 exposure was associated with a significant increase in pregnancy rates. In a population living in a highly polluted area in Italy, we added suggestive evidence of a negative association between ART outcomes and PM10 exposure after controlling for known risk factors for ART success rate.