Normal monthly menstruation does not necessarily lead to ovulation, which mostly occurs during puberty and menopause. If the neuroendocrine functions regulating the reproductive system are not mature during puberty, or if the patient suffers from various diseases such as gonorrhea or ovarian failure, it can lead to anovulatory menstruation. Ovulation is not a fixed date, but is considered by modern medicine to occur approximately 14 days before the onset of menstruation. The presence or absence of follicles can be visualized by ultrasound examination, and the presence or absence of ovulation can be detected by ovulation test paper several times in a row.