The purpose of this study is to determine if Human Epididymis Protein 4 (HE-4) levels vary during the menstrual cycles in ovulatory women. HE-4 is a sensitive serological marker that is elevated in certain ovarian and endometrial cancers and can aid in the diagnosis of these malignant conditions. In order to optimize the utility of HE4 as a tumor marker in premenopausal women, its expression in the normal menstrual cycle needs to be characterized. We hypothesize that HE-4 levels do not vary in the menstrual cycle.