Under normal circumstances, the best time for ovulation testing usually starts on the 10th day of menstruation. If the menstrual cycle is regular, usually around the 7th day of menstruation, one follicle in the follicular cluster develops preferentially into the dominant follicle, while the other eggs gradually degenerate and occlude. As the follicle develops and grows, it can increase in size to about 20mm before ovulation. If ovulation is detected by ultrasound, it is recommended to start testing on day 10 of the menstrual cycle, every other day, and more frequently as it approaches 18mm, depending on the ultrasonographer’s recommendation for the next test. Testing should be continued after ovulation. If the ultrasound reveals the disappearance of the dominant follicle, the formation of blood bodies and a small amount of fluid in the rectal recess of the uterus, this is indicative of ovulation. Therefore, intercourse can be appropriately scheduled between the time the follicle develops to about 18-20mm and 12 hours after ovulation to increase the chance of conception.