The safe period of menstruation is the 1st-7th days of menstruation and the 4-5 days before menstruation; ovulation in women with regular menstrual cycle is around 14 days before the next menstrual period. Ovulation usually occurs in the middle of the menstrual cycle, about 14 days before the next menstrual period. Having intercourse 2-3 days before and after ovulation increases the chance of sperm meeting the egg. A healthy sperm can survive for 2-3 days after reaching the uterine cavity, but its fertility can only be maintained for 1-2 days. Therefore, in most cases, intercourse during the 2-3 days before and after ovulation is the time when a woman has the best chance of conceiving, which is called the fertile period. On days 1-7 of the menstrual cycle and 4-5 days before the menstrual cycle, ovulation does not occur in the ovaries, and even if ovulation has occurred, the eggs are basically dead, so this period is called the absolute safe period. In addition, for couples who want to prevent pregnancy, it is important to take good contraceptive measures, such as taking birth control pills, placing intrauterine devices, and wearing condoms.