It is possible for a woman to become pregnant if she has intercourse a week before her menstrual period. There is no absolute safe period for women. Even though the week before menstruation is a safe period for women, ovulation can be affected by many factors, such as changes in a woman’s mood, stress from school and work, or sudden drops in outside temperatures, and because of geographical changes. Ovulation can occur within the safe period, so it is possible to get pregnant during the safe period. If a woman’s menstrual cycle is relatively short, around 21 days, and her menstrual period is relatively long, around seven days, the week before her period coincides with ovulation, and the chances of ovulation are relatively high at this time. Therefore, the chance of getting pregnant when having intercourse without contraception is very high, and if there is no intention of getting pregnant, emergency contraception must be taken.