ALDH1A1 and endometriosis: Consistent with the differences in the eutopic endometrium of women with and without endometriosis, we have previously shown distinct differences in menstrual effluent (ME) and menstrual effluent-derived stromal fibroblast cells (ME-SFCs) obtained from a small cohort of women with endometriosis compared to healthy controls, including impaired stromal cell decidualization and reduced expression of ALDH1A1 and other genes associated with the retinoic acid pathway (21).