The main reason is that at this time the period may not be clean or just clean, most women’s periods are clean in 3-7 days, the follicles have not yet reached a dominant state, so at this time intercourse will not be pregnant. Do not have sexual intercourse when your period is not cleared, as it is likely to lead to bacterial infection of the reproductive tract. In addition, it is recommended to have intercourse 2-3 days after your period is completely clean, as this will protect the physical and mental health of the woman. If you have intercourse on the fifth day of clean menstruation, the possibility of pregnancy is higher at this time, because the period itself is clean for 3-7 days. If you have intercourse on the fifth day of menstruation, which is clinically the 10th-12th day of menstruation, you are more likely to get pregnant if your menstrual cycle is relatively short.