Ovulation disorders are one of the main causes of infertility in married women of childbearing age. How to accurately observe drug-induced follicular development and estimate the period of ovulation, and reduce the occurrence of a series of complications due to drug-induced ovulation, clinical ovulation monitoring methods include basal body temperature, cervical mucus score, blood estrogen or progesterone measurement, and blood or urine LH peak measurement, but none of these methods can monitor the number, location and development of the dominant follicle However, none of these methods can monitor the number, location and development of the dominant follicle, nor can they accurately indicate follicular maturation and follicular rupture and ovulation. However, these methods cannot monitor the number, location and development of the dominant follicle. The high-resolution vaginal probe is almost in direct contact with the scanned organs, close to the cervix and vault, without filling the bladder, and is not affected by intestinal gas interference or abdominal wall sound attenuation, so that the sonogram of the pelvic organs is clear, especially the endometrium and ovaries are more clearly observed, and the monitoring can be repeated, safe and reliable, with high accuracy. The changes in the ultrasound images of the follicles can be monitored in a more comprehensive way. The endometrium of the uterus is thin in the early stage of follicles, with a thickness of about 3-6 mm, and thickens as the follicle grows and the estrogen level gradually increases. When the follicle reaches maturity, the thickness of the endometrium generally reaches 10-14 mm. according to the echogenicity of the endometrium, it can be divided into type A endometrium (endometrial echogenicity is lower than the uterine wall echogenicity with obvious trilinear sign), type B endometrium (endometrial echogenicity is the same as myometrial echogenicity), and type C endometrium (endometrial echogenicity is higher than myometrial echogenicity). 2. Follicle size: When measuring follicles, the long diameter and the transverse diameter perpendicular to the follicle are measured after displaying the largest follicular section and the average is taken. In a natural cycle, only one follicle usually develops to maturity and the rest are atretic. When the follicle reaches 10 mm in diameter, it becomes the dominant follicle, which is usually present in only one side of the ovary during the natural cycle. The growth rate of the dominant follicle is about 1-2mm/d, and the growth rate of the follicles near ovulation can reach 2-3mm/d. When the follicle reaches 18-20mm in diameter, it becomes a mature follicle, oval or round, with an echogenic area inside, with a clear border and some tension, often protruding from the surface of the ovary. 3. Signs of ovulation: (1) disappearance of mature follicles, most common; (2) shrinkage of follicles, the original mature follicles are significantly reduced in diameter (greater than 5mm) and irregular in shape; (3) effusion in the rectal recess of the uterus, which occurs in about 40% of cases; (4) endometrium shows a secretory phase reaction and the fractal transformation to C-type endometrium. Ovulation monitoring time 1. Ovulation monitoring in natural cycle: for 28-30 days menstrual cycle, the first vaginal ultrasound monitoring should be started from the 8th-10th day of menstruation; for irregular menstruation, monitoring can be started from the increase of leukorrhea, when the dominant follicle is <10mm, monitor once every 3 days; when the diameter is 10-14mm, monitor once every 2 days; when the diameter is ≥15mm, monitor once a day. It is also combined with menstrual cycle, endometrial thickness, BBT, cervical mucus and urinary LH semi-quantitative measurement to predict ovulation time. If there is liquid darkness on the ovary larger than 1cm or ovarian occupancy, the ovulation will not be promoted in the cycle. 4. Follicular manifestations of abnormal follicular cycles 1. anovulatory cycle: no change or no follicular development after continuous observation of small follicles slightly developed in both ovaries. 2. Small follicular cycle: slow follicular growth with <17 mm at the time of follicular ovulation. 3. Unruptured follicular luteinization syndrome (LUFS): normal follicular growth and development, but ovulation does not occur at the time of ovulation, with dotted or linear echogenicity in the echogenic zone of the follicles, showing luteinization changes.