For women with regular menstrual cycles, the safe period is 7-10 days before the onset of menstruation. The safe period is only relative to ovulation and is not absolutely safe. If you have a regular menstrual cycle, you can use the safe period to prevent pregnancy. However, if the menstrual cycle is not regular, the safety period is not fixed, and contraception through the safety period will lead to contraceptive failure and a very high chance of unwanted pregnancy, which has a greater impact on women’s health. In order to be safe, if you are not ready to get pregnant and have children, it is best to take birth control when having intercourse by placing an intrauterine device or wearing a condom to prevent unwanted pregnancy.