Most people think that having intercourse during the safe period will not result in pregnancy, but this is not the case, as there is a possibility of pregnancy during the safe period, so it is not safe or desirable to use contraception during the safe period. The safe period is a period of time when a woman is not fertile, based on her ovulation period and the survival time of sperm and eggs in the female reproductive tract, so intercourse is chosen during this time to achieve the purpose of contraception. Generally speaking, eggs can survive for 1 to 2 days after ovulation and sperm can survive for 2 to 3 days in the female reproductive tract. Therefore, if you have sex 2 to 3 days before ovulation and 1 to 2 days after ovulation, you are likely to conceive, and this period is called the fertile period. Ovarian ovulation is usually within 2 days before and after the 14th day of menstruation, so the safe period is about 10 days after menstruation, and after the 20th day of menstruation until the next menstruation, the closer to the menstruation period, the greater the possibility of contraception. However, this method of calculation is often unreliable because the timing of ovulation in women is affected by the external environment, the climate, her emotions, and her state of health, resulting in delayed or early ovulation, and the possibility of additional ovulation. It is difficult to accurately calculate the maximum survival time of the sperm and egg, so it is not always safe to say that the safe period.