If no conception occurs after ovulation, menstruation will occur in about 14-15 more days, the exact time varies depending on individual’s body type. If ovulation is normal, the luteal phase is after ovulation. On the 7th-8th day after ovulation is the peak of luteal function, and on the 9th-10th day the corpus luteum begins to degenerate. After the luteal body declines, the endometrium is affected by the hormone level in the body and shedding occurs, i.e. menstruation comes. If conception is successful after ovulation, influenced by the level of progesterone in the body, the corpus luteum may become the corpus luteum of pregnancy, and menstruation will not come and menopause occurs. Normal menstruation has a certain regularity and cycle, usually the cycle is between 21-35 days, with an average of 28-30 days, but there are very few women whose menstrual cycle is between 45 days and 2 months. After ovulation, if the luteal phase is shortened due to insufficient luteal function, the menstrual cycle will also be shortened and an early onset of menstruation may occur.