Pharmacological ovulation promotion has been widely used to treat ovulation disorders with great success. In normal ovulation cycles, follicular images are usually visible from day 5-7 of the cycle, and the incidence of multiple follicles is 35%-80%. Multiple follicles are distributed in one or both ovaries, extruding and deforming each other. Many authors report that the daily growth rate of follicles and the maximum diameter of follicles before ovulation in induced cycles are not significantly different from those in natural cycles, while some authors suggest that follicle development is significantly greater in induced cycles than in natural cycles. Ovulation occurs 36-48 hours after HCG administration, and multiple follicles may rupture on the same day or 1-2 days apart, respectively. The ovulation and luteal phases of the ovulatory cycle are not significantly different from those of the natural cycle. Sonographic manifestations of drug-induced follicular maturation and ovulation 1. Clomiphene: also known as clorophobene, its follicular phase is similar to or slightly longer than that of the natural cycle, with most of the main follicles exceeding 1 and usually more than 1-2 follicles mature. Their mature follicles are larger in diameter than natural cycles, averaging about 23 mm (18-25 mm). Ultrasound monitoring of follicle development needs to be performed continuously and should be done daily for 2-3 days near ovulation. 2. Urinary gonadotropin: contains follicle stimulating hormone and luteinizing hormone, or ovulation induction therapy with pure FSH. Its follicular ultrasound presentation can be irregularly round, oval, triangular or polygonal, with multiple follicles in the ovary of different sizes. The follicles further enlarge with HCG, with an average follicle diameter of about 25.6 mm (18-30 mm) and a deep liquid dark area in the rectal fossa after ovulation. The follicles were slow growing, irregular, with thick follicular walls. The follicles stopped growing below 17 mm in diameter, and there were no signs of mature follicles and follicular ovulation that met the monitoring criteria, and the follicles were gradually atrophied and atretic under continuous observation. The follicles were not ruptured but continued to grow after the ovulation day, with a diameter range of 30 mm-50 mm, forming a cyst with thin and smooth wall and high tension, which continued to disappear until the next menstrual cycle. The follicles are mature and there are signs of mature follicles that meet the monitoring criteria, no signs of follicular ovulation, and no signs of ovulation after HCG administration. Sonographic manifestations of ovarian hyperstimulation syndrome Bilateral ovarian enlargement with multiple follicles and corpus luteum cysts with interstitial ovarian edema.