RecruitingPhase 2ProcedureMammogram Pretreatment With Ulipristal AcetateThis phase II trial tests whether taking ulipristal acetate prior to a mammogram decreases breast density for people with a history of dense breast tissue. One limitation to breast cancer screening with mammography is dense breast tissue, which decreases the sensitivity of screening as breast density masks cancer and precancerous lesions. Ulipristal acetate lowers the amount of progesterone made by the body which may temporarily decrease the density of the breast tissue, allowing for a more accurate mammogram for people with dense breast tissue.