The safe period is the first seven days of the first day of menstruation and the next eight days belong to the safe period, when the chance of pregnancy is lower, but this statement does not apply to everyone. The safe period for women with a 28-day menstrual cycle is seven days before and eight days after the onset of menstruation, and not all women’s menstrual cycles are 28 days, so this statement has a strong limitation and does not apply to everyone. Even if the menstrual cycle for 28 days of women, in this so-called “safe period” is not absolutely safe. Even if a woman has a 28-day menstrual cycle, the so-called “safe period” is not absolutely safe, because even if she has intercourse during the safe period, the stimulation of intercourse may lead to abnormal ovulation, which may result in an unplanned pregnancy. Moreover, the menstrual cycle can be affected by the environment, health, emotions and so on, which can change the safe period, and women may miscalculate the safe period and get pregnant. Although the probability of this kind of unwanted pregnancy is very low, it is still important to take proper contraceptive measures during the safe period. Safe period contraception is one of the least safe forms of contraception, so it is not recommended. Instrumental contraception such as birth control rings and male condoms can be used.