The luteal phase is the phase of the menstrual cycle following ovulation. It is therefore the second half of the cycle, which releases the egg from the ovary and lasts until the start of the next menstrual bleeding.
During the luteal phase, the lining of the uterus (endometrium) prepares to receive the eventual egg which, if fertilized, will nest in the endometrium. If fertilization does not take place, the levels of the hormones progesterone and estrogen decrease, causing the uterine lining to detach and subsequent menstrual bleeding.
The luteal phase is therefore a key part of the menstrual cycle, allowing the uterine lining to prepare to receive the fertilized egg and subsequently ensuring either the continuation of pregnancy or the shedding of the uterine lining during menstruation.
