The luteal phase is a part of the menstrual cycle that occurs after ovulation and before the start of menstruation. It typically lasts about 14 days. During this phase, the corpus luteum, which forms from the follicle that released an egg, produces hormones like progesterone. This hormone helps prepare the uterus for a potential pregnancy. If fertilization does not occur, the corpus luteum breaks down, leading to a decrease in progesterone levels. This drop triggers the shedding of the uterine lining, resulting in menstruation. The luteal phase is crucial for reproductive health and can affect menstrual cycle regularity.