The 5th day after menstruation is not necessarily a safe period, depending on the actual situation of the individual. Usually, if a woman’s menstrual cycle is regular, the menstrual cycle is around 28~35 days, the ovulation date is around 14 days before the next menstrual period, the 5 days before and 5 days after the ovulation date belong to the vulnerable period, and the time other than that belongs to the safe period, therefore, the 5th day after menstruation usually belongs to the safe period. However, if a woman’s menstrual cycle is irregular, or her menstrual period is relatively short, with a duration of less than 28 days, and the duration of her period is relatively short, the 5th day after her period may be a vulnerable period, and some women may even have entered the ovulation period, and if they do not pay attention to contraception during this period, the chances of getting pregnant will be relatively high. If a woman does not intend to get pregnant, it is recommended that she use contraception no matter when she has intercourse to avoid an unwanted pregnancy. If the phenomenon of delayed menstruation, delayed for more than a week, it is recommended to actively go to the regular hospital, to clarify the cause, and then targeted treatment.