Aunt that is, menstruation, women do not have menstruation for more reasons, including pregnancy, endocrine disorders, polycystic ovary syndrome, etc. The specific situation is analyzed as follows: 1. Pregnancy: The formation of menstruation is related to the endometrium losing the support of estrogen and progesterone to shed and bleed. And when a woman is pregnant, in order to maintain the normal growth and development of the gestational sac, the estrogen and progesterone in the body will rise. As there is no hormone retreat, there is no endometrial exfoliation and bleeding, and then there is no menstruation. 2. Endocrine disorders: bad habits, such as often stay up late, irregular work and rest. Or often eat spicy and stimulating food and cold food, it may lead to endocrine disorders, menstruation does not appear. 3. Polycystic Ovary Syndrome (PCOS): The main manifestations of PCOS patients include scanty menstruation, which is characterized by absence of menstruation. Besides that, there are low menstrual flow, amenorrhea and acne. It may also cause infertility because of its prolonged absence of ovulation. In conclusion, there are many reasons why women do not have menstrual periods. Women who experience the above symptoms are advised to consult a doctor promptly to clarify the cause of the problem and then under the guidance of the doctor to carry out targeted treatment.