Women usually have a safe period 5 days after menstruation or 7 days before their period, and it is not easy to get pregnant during this period. For women with regular menstrual cycles, ovulation usually occurs about 10-14 days after menstruation, i.e. about 14 days before the next menstrual period. Except for ovulation and menstruation, the rest of the time is considered safe. Although the chances of pregnancy are lower when having intercourse at times other than ovulation, ovulation can be affected by many factors and is not fixed. When a woman is stressed, emotionally distressed or has an endocrine disorder, ovulation may occur earlier or later and the presumed safe period may not be accurate. Therefore, contraception based solely on the safety period is not reliable and may also lead to unwanted pregnancy. Therefore, women who have intercourse when they are not ready to get pregnant must do a good job of contraception to avoid harm to their bodies due to abortion of unwanted pregnancy.