Menstruation is the cyclical shedding of the uterine lining by the hormones secreted by the ovaries after the ovarian function of a woman has matured. Most women will have their first menstrual period around the age of 11-13 years old, while a few will need to be 15 years old, and after their menstrual period has established a regular pattern, they will basically have their menstrual period once a month, and each time they have their menstrual period, they will have their menstrual period for around 3-7 days. Regular menstruation also represents a woman’s ovarian function, and when a woman has menstruation, she is fertile. If a woman with regular menstruation does not want to have children, she needs to take contraceptive measures and should not have intercourse during menstruation.