Most women can only have a chance to conceive during ovulation, which is the basis for conception. Under normal menstruation, a woman ovulates from the first day of her next period, counting backwards 14 days to the day of ovulation, and the interval of 5 days before and 4 days after the day of ovulation is the ovulation period. Under normal circumstances, a mature egg is expelled from the ovary into the abdominal cavity every menstrual cycle. After ovulation, the egg is in a waiting state and will not become fertilized if no sperm meets it. The egg is viable for 24-48 hours and the sperm is viable for 24-72 hours. If the egg is in a waiting state, pregnancy is possible on the day of intercourse. If you have sex before ovulation, fertilization can be completed on the day of ovulation, just as the sperm reaches the location of the egg. However, some women ovulate irregularly and may ovulate twice a month, so it is not very accurate to rely on the projected date to determine whether ovulation is taking place or not.