According to About.com, the luteal phase is the menstrual phase after the follicular phase. This places the luteal phase on the 14th day of a menstrual cycle. The luteal phase is also known as the premenstrual or ovulatory phase.
About.com states that estrogen and progesterone levels increase in a woman’s body to provide an endometrial uterus lining for the embryo during the luteal phase. The luteal phase continues until the first day of menstruation, which means that conception did not occur. As the luteal phase reaches its conclusion, estrogen and progesterone levels lessen and the uterus lining that was prepared during the luteal phase begins to shed.