For ultrasound ovulation monitoring, you can start with an ultrasound 2-3 days after your period to initially see how the follicles are doing. Depending on the condition of the follicles, an appointment will be made for when the next ultrasound will be done, usually 3-5 days apart the next ultrasound is needed. The follicles develop and ovulate on about the 14th day before the next menstrual period. Therefore, the whole menstrual cycle is monitored by ultrasound at least 3-4 times to basically monitor the discharge of mature follicles. Mature follicles are 1.8-2.5 cm in size and the chances of pregnancy are high if you have intercourse within 24 hours before and after the follicles are expelled.