Generally, the day of ovulation is the 14th day of menstruation, and the ovulation period is the day of ovulation plus the 3 days before and after the day of ovulation. In addition to the menstrual period and ovulation, the safety period is the period of the menstrual cycle. The ovulation period and the safety period of a woman are specific to her ability to conceive. For women of childbearing age with a normal menstrual cycle of 28 days, the day of menstruation is the first day of the menstrual cycle and the 14th day is the day of ovulation. Since the egg survives in the body for 12-24 hours after ovulation and the sperm can survive for about 72 hours after entering the body, with a maximum of 5 days, including the survival time of the sperm, the 3 days before and after ovulation have a chance of conception, so this period is called the ovulation period. The rest of the time, excluding ovulation and menstruation, has a very low chance of conception and is called the safe period. Therefore, women who need to prepare for pregnancy can use the ovulation period to have intercourse to increase their chances of conception. However, the success rate of contraception during the safe period is only 60-70% and there is a possibility of unintended pregnancy, so it is recommended to consult a doctor for safe contraception.