First of all, there is no absolute safe period, the relative safe period is usually 7 days before menstruation and 8 days after the end of menstruation. The correct calculation of a woman’s menstrual cycle is the sum of the time from the first day of menstruation to the day before the next menstrual period. For women with regular menstrual cycles, ovulation usually occurs about 14 days before the next menstrual period, and 4-5 days before and after ovulation are easy to conceive, while the rest of the time is the relatively safe period. In reality, women’s mood changes, dietary habits, irregular work and rest will affect the date of ovulation, so women’s safe period is not completely accurate, even if the usual menstrual rules of the women, faced with a sudden change in psychology, environment, etc., endocrine disorders can occur, resulting in delayed or early menstruation, the safe period will also change. If you want to use contraception, it is recommended that you use condoms and other tools to prevent pregnancy.