The 6th day after the end of menstruation is not a safe period. The menstrual period usually lasts for 3-7 days, and the 6th day after the end of menstruation is equivalent to the 9th-13th day of the menstrual cycle. Most women have already entered the ovulation period at this time, and if they do not take contraceptive measures during sex, the possibility of unintended pregnancy after coitus is relatively high. The safe period and the ovulation period are calculated by the menstrual cycle and the time of menstruation. The safe period is usually on days 1-10 and 21-30 of the menstrual cycle, that is, within 10 days before the next menstrual period. A woman’s menstrual cycle is not completely fixed, and the day of ovulation may be advanced or pushed back, and the safe period is also not fixed. If the menstrual cycle is shortened, the safe period before ovulation will be shortened accordingly. Relying solely on the safe period for contraception does not provide a definitive contraceptive effect, and this method of contraception is generally not recommended.