Delayed menstruation in girls may be related to physiological reasons such as mental tension and pregnancy, as well as infectious diseases such as chronic cervicitis and non-infectious diseases such as ovarian dysfunction. 1. Physiological reasons: women who have sex first need to clarify whether the delayed menstruation is related to pregnancy; in addition, mental tension and life stress can also lead to delayed menstruation. 2. Pathologic causes: (1) Infectious diseases. When a woman suffers from chronic endometritis, chronic cervicitis, etc., it can cause delayed menstruation. (2) Non-infectious diseases. Excessive weight loss may cause ovarian dysfunction, leading to delayed menstruation; hyperthyroidism may affect ovarian function, leading to delayed menstruation; severe anemia and malnutrition may also cause delayed menstruation. In addition, oral progesterone, dydrogesterone and other progestin drugs can also cause delayed menstruation. When a woman’s menstruation is delayed for more than 7 days, the cause can be clarified under the guidance of a doctor for active treatment.