The 21-day ovulation period is the period that includes 5 days before the day of ovulation, the day of ovulation and 4 days after the day of ovulation, so the 21-day ovulation period refers to the 2nd day to the 11th day of the menstrual period. Ovulation refers to the period when the follicle develops and matures and is discharged from the ovary, the time includes 5 days before the day of ovulation, the day of ovulation and 4 days after the day of ovulation, a total of 10 days of time, the day of ovulation usually occurs about 14 days before the next menstrual period, if the monthly menstrual cycle is 21 days, the ovulation period is the period of menstruation between the 2nd day and the 11th day. Ovulation generally has no obvious discomfort symptoms, some women will feel abdominal cramps, increased leukorrhea, there may also be bloody leukorrhea, at this time the uterine lining is thicker, the fertilized egg is easy to bed, it is easier to conceive.