Flexi Says: Progesterone helps prepare the endometrium for pregnancy. If an egg has been fertilized, it will soon start producing a hormone which helps maintain the corpus luteum. As a result, the corpus luteum will continue producing progesterone and maintain the endometrium. If the egg has not been fertilized, the corpus luteum will disintegrate and stop producing progesterone. Without progesterone, the endometrium will break down, detach from the uterus, and pass out of the body during menstruation.
