Secular trends in semen parameters among men attending a fertility center between 2000 and 2017: Identifying potential predictors.

•Sperm concentration and count declined 37% and 42%, respectively, between 2000 and 2017 among men attending a fertility center in Boston.•Total motility and morphologically normal sperm declined 15% and 16% over the 17 year study period, respectively.•When reproductive factors were included in the model, the downward trends in semen parameters were attenuated between 29% and 54%.•The downward trends in sperm concentration and morphology were attenuated by 19% when including the DEHP and non-DEHP metabolites, respectively.