The best time to monitor the follicles is usually from the 10th day of menstruation, and then once a day or every other day, depending on the development of the follicles. If your menstrual cycle is regular and you have your period once a month or so, start counting from the first day of your period and go to the hospital on the 10th day of your period for vaginal ultrasound to monitor your follicles. Normally, you should be able to see the dominant follicle when you have a vaginal ultrasound on the 10th day of your period. At this point the follicles are growing at a rate of about two millimeters per day, and can be monitored as often as every other day or once a day, depending on the size of the follicles. If the follicle is 18 millimeters or more during follicle monitoring, it means that the follicle has matured and may ovulate at any time. From this point on, you can adopt the frequency of every other day intercourse, will increase the chances of pregnancy. If menstruation is irregular, dynamic monitoring is required to determine the monitoring time based on the size of the follicle and cannot be generalized.