If the menstrual cycle is regular, ultrasound monitoring of ovulation usually starts on the 8th-10th day of the menstrual cycle, usually on the 5th-6th day of the menstrual cycle, when the follicle diameter is 5-7 millimeters. The follicle will then continue to grow, and when the follicle reaches 10 mm in diameter on day 10 of the menstrual cycle, the 1st follicle monitoring can be done at this time, and the next visit will be decided based on the results of the examination, which usually takes 3-4 days before the monitoring is done again. When the follicles develop to 15 mm, you need to go to the hospital every day to do follicle monitoring, most of the follicles will grow to 18 mm for the dominant follicle, at any time there may be ovulation needs to be arranged for coitus, coitus in the period of ovulation relative chances of pregnancy will be greater. You can also use ovulation test paper to monitor ovulation, you need to use ovulation test paper to monitor every day at the end of the menstrual cycle for about 1 week, when the strong positive gradually turned weak, indicating that ovulation is about to occur.