If a woman has her period on the 20th and her menstrual cycle is regular, the safe period is between the 25th and 30th of the month, and 5-6 days before her next period. The safe period and the risk period are relative. The safe period means that the woman’s ovaries do not ovulate during this period, so no egg and sperm will be combined after sex, which will not easily lead to pregnancy. But safety is not absolutely safe, sometimes there may be early ovulation or delayed ovulation due to changes in the hormones secreted by women’s ovaries. If a woman does not want to get pregnant or have a baby, it is safer to use a contraceptive method such as a penis condom or an intrauterine device (IUD). If you want to get pregnant and have a baby, it is best to have intercourse in the middle of two periods, i.e. ovulation, to increase the chances of pregnancy.