If the patient has had regular periods in the past, then generally speaking, 5 days after the menstrual cycle or 7 days before the menstrual cycle is a safe period and is less likely to result in pregnancy. However, the safe period is only relatively safe, not absolutely safe from pregnancy. The safe period is divided into the safe period before ovulation and the safe period after ovulation. The 5 days just after menstruation is the safe period before ovulation, and the 7 days from the end of ovulation to the next period is the safe period after ovulation, i.e. the week before menstruation is the safe period after ovulation. However, some women ovulate twice a month, or usually have irregular menstrual cycles, resulting in irregular ovulation, and even if they have intercourse during the so-called safe period, they may still get pregnant. Therefore, if a woman is not prepared to get pregnant, it is recommended to take effective contraceptive measures even during the safe period to avoid unwanted pregnancy.