Progesterone, a type of female sex hormone that belongs to the class of steroid hormones known as progestins, plays an important role in the development of oral contraception. Progesterone is produced in the ovaries, adrenal glands, and placenta when women become pregnant. In the menstrual cycle the ovary incessantly alternates two phases: the follicular phase, characterized by the presence of maturing follicles, and the luteal phase, governed by the presence of the corpus luteum. Ovulation occurs between these phases. The corpus luteum, which forms through luteinization of the ruptured follicle after ovulation, secretes large amounts of progesterone and small amounts of estrogen. Progesterone acts on progesterone receptors (PR) which come in two isoforms: PR.A and PR.B. Binding of progesterone to receptors leads to dimerization. “Dimers bind to DNA at specific progesterone response elements on the promoters of progesterone-responsive genes and regulate transcription” (Ruenitz, 2010, p237) directly or associated with co-activators or co-repressors. It increases the number of blood vessels and secretory glands in the estrogen-stimulated endometrium to create a hospitable and nourishing lining for implantation of a fertilized egg and keeps the endometrium quiescent by reducing the contractility of the uterus. Furthermore, progesterone also acts on kiss1 neurons of the hypothalamic arcuate nucleus (ARC) and indirectly inhibits the pulsatile release of gonadotropin-releasing hormone (GnRH) and thereby suppresses the secretion of luteinizing hormone (LH) and follicle-like hormone. stimulant (FSH) from the anterior pituitary gland. These inhibitions help prevent new follicular maturation and ovulation during the luteal phase. Levonorgestrel (LNG) is a second-generation synthetic progestin. This is... half of the article... fepristone increases prostaglandin secretion by decidual cells and induces prostaglandin accumulation by inhibiting prostaglandin dehydrogenase. (Spitz, 2009) Furthermore, Mifepristone also increases the sensitivity of the myometrium to prostaglandins. In early pregnancy, mifepristone initiates cervical maturation by stimulating the release of nitric oxide (NO) and the expression of inducible NO synthase in the cervix. (Spitz, 2009) In addition to abortion, mifepristone is also indicated for many conditions such as uterine fibroids, endometriosis, etc. Mifepristone also exerts contraceptive potential as some studies have found that ovulation is inhibited with daily mifepristone doses of 2 mg or higher. (Spitz, 2009) However, mifepristone has slow clinical development due to political, legal, and religious controversies regarding its ability to induce medical abortion. (Spitz, 2009)