Ultrasound monitoring of ovulation is the use of vaginal ultrasound or abdominal ultrasound to monitor the development of follicles and the ovulation process in a woman’s body. Most women use vaginal ultrasound because it is more accurate and because they do not have to hold their urine. Often a combination of vaginal ultrasound and abdominal ultrasound is used to produce more accurate results. For women whose menstrual cycle is 28-30 days, monitoring is usually started on day 10 of the menstrual cycle. For follicles less than 10 mm in diameter, monitoring is usually performed once every 3 days. For follicles between 10-14mm in diameter, ovulation monitoring is required once every 2 days. If the follicle diameter is greater than 15mm, monitoring is usually done once a day. In addition, the timing of sexual intercourse needs to be guided by a combination of the growth rate of the follicle and the thickness of the endometrium. Intercourse is guided when the follicle has increased to 18-20mm, depending on the patient’s condition. Ultrasound monitoring of ovulation is currently the more accurate and commonly used monitoring method.