Menstruation usually occurs 14 days after the day of ovulation, after which the corpus luteum forms and degenerates, and luteal function is limited to 14 days, after which menstruation occurs and a new cycle begins. Ovulation usually occurs about 14 days before the next menstrual period. After ovulation in women of childbearing age, the follicular granulosa cells and follicular membrane cells invade inward, and connective tissue wraps around them to form the corpus luteum. If the egg is not fertilized, the corpus luteum gradually degenerates and its function is limited to 14 days. After the corpus luteum declines, menstruation occurs, a new menstrual cycle begins, and new follicles begin to develop in the ovary. The mechanism by which the corpus luteum function is limited to 14 days is currently unknown, and may be related to its secretion of estrogen luteolysis. It is often used in clinical practice to predict the day of ovulation and to guide fertility, etc. If there is any discomfort, it is recommended to consult a doctor. If there is any discomfort, it is recommended to seek medical advice and treatment promptly.