Vaginal ultrasound is a test performed to find out the condition of the female reproductive organs such as the ovaries and uterus; it measures the size of the uterus, the thickness of the endometrium, the size of the ovaries, the size and number of follicles and the presence of reproductive system disorders (e.g. fibroids, endometrial polyps, uterine malformations, ovarian masses, pelvic effusion, etc.). The use of ultrasound to detect ovulation allows dynamic observation of follicular development and ovulation to determine the timing of ovulation, ovarian function and to detect certain diseases such as follicular luteinization non-rupture syndrome. Ovulation monitoring by vaginal ultrasound I. Key points of monitoring: 1. endometrium 2. follicle size 3. basal follicle count II. timing of ovulation monitoring 1. natural cycle ovulation monitoring For menstrual cycle of 28-30 days, the first monitoring should be started from the 10th to 12th day of menstruation; for irregular menstruation, monitoring can be started from the increase of leucorrhea. 2.Drug for ovulation cycle Generally, the medication is started on 3-5 days of menstrual cycle. Before medication, vaginal ultrasonography should be performed to understand the ovarian condition, and after medication, the program should be adjusted according to the size of the follicles, and HCG should be used to induce ovulation if necessary. The follicular manifestations of abnormal cycles 1. anovulatory cycles No change in bilateral ovaries or no follicular development is observed continuously. 2.Small follicular cycles Continuous observation of slow follicular growth and failure to reach normal mature follicle size at ovulation. 3.Luteinization syndrome with unruptured follicles (LUFS) The follicles grow and develop normally, but ovulation does not occur during ovulation, and there are dotted and linear echogenicity within the echogenic zone of the follicles, showing luteinization changes.