The safe period of seven days before and eight days after refers to a specific period of time before and after a woman ovulates and before and after the onset of menstruation. The period of time from the first day after the end of ovulation to the day before the next menstrual period is generally seven days, and is referred to as the first seven days. The period from the first day after the end of menstruation to the day before ovulation begins is generally eight days and is known as the second eight. The period of time between the first day of menstruation and the last eight days is known as the safe period because there is no ovulation, so the chances of getting pregnant are lower when you have intercourse without any contraception, so it is known as the safe period. The safe period is not necessarily safe, after all, women’s menstruation is not necessarily regular, ovulation is not necessarily regular. Women who usually have relatively regular menstrual periods may also be affected by other external factors such as mood swings, overwork, irregular work and rest, and so on. Therefore, couples who do not want to have a baby for the time being are advised to take regular contraceptive measures.