Usually for women with regular menstruation, 7 days before and 8 days after menstruation are safe periods, because at this time the follicles are in the developmental stage and not yet mature, so the follicles will not ovulate, so the chances of pregnancy are low, so it is called a safe period. However, the safe period is relative and not absolute. It is greatly influenced by a woman’s menstrual cycle and period. For a woman who has her period once in 28 days, her ovulation period is about 14 days before her next period, and the rest of the time is the menstrual period and the safety period. However, if a woman has irregular periods, her ovulation period will be different. If she still has intercourse during the safe period calculated by the above method, she will easily conceive. Therefore, if a woman wants to take the safe period method of contraception, she needs to be alert to the possibility of contraceptive failure, and to improve the chances of success, it is recommended to use more effective contraceptive methods such as condoms.