CYP19A1 and Infertility: Compared to women with tubal or unexplained infertility undergoing ARTs, reduced aromatase activity in granulosa cells as well as reduced expression of the cytochrome p450 family 19 subfamily A member 1 (CYP19A1) gene (that encodes aromatase) in cumulus cells has been shown in infertile women with endometriosis by in vitro studies (35,36).