Polycystic ovary syndrome (PCOS) is an extremely complex endocrine disorder common in women of reproductive age and is one of the most common causes of anovulatory infertility. In recent years, with the development of diagnostic tools, the understanding of this disease has become more advanced and progressed, making the treatment more targeted. In 1935, Stein-Leventhal first summarized the syndrome as amenorrhea, hirsutism, obesity and cystic enlargement of bilateral ovaries, called Stein-Leventhal syndrome. 1962, Goldzieber and Green summarized 1079 cases and recognized many atypical signs in the disease, such as no hirsutism and even ovulatory function, etc. In 1990, the National Institutes of Health (NIH) meeting listed the diagnostic criteria for PCOS: clinical and/or biochemical evidence of hyperandrogenism, prolonged anovulation, with or without ultrasound diagnosis of polycystic ovaries. However, the diagnostic criteria vary considerably between countries and regions, so it is not possible to compare data from national studies. The methodology of all studies is controversial. In 2003, the European Society for Human Reproduction and the American Society for Reproductive Medicine held a joint meeting in Rotterdam, the Netherlands, where new diagnostic criteria for PCOS were adopted: two or more of the three manifestations of prolonged anovulation, hyperandrogenism and polycystic ovaries must be present for the diagnosis to be confirmed, except for other related diseases. The details are as follows: 1. Long-term anovulation: also known as persistent anovulation, manifested as amenorrhea or dysfunctional uterine bleeding. Serum progesterone of 18 nmol/L (5.6 ng/ml) on day 20-24 of the normal menstrual cycle is considered as an indication of ovulation. Long-term anovulation is due to dysfunction of the pituitary-hypothalamic-ovarian (H-P-O) axis with follicular dysfunction, and follicles of different growth and developmental stages are seen in the ovaries. 2. Hyperandrogenism: exclude related diseases, clinical symptoms and/or biochemical tests suggest hyperandrogenism. Clinical symptoms: Hirsutism is the most common, but it can also be manifested only as acne or even alopecia areata. Biochemical tests: Current laboratory tests cannot accurately distinguish between different types of androgens. 3. Polycystic ovaries: Ultrasound shows that polycystic ovaries refer to “at least 12 small follicles of 2-9 mm in diameter and/or increased ovarian volume (>10 ml) on each side of the ovary”. The definition does not involve subjective human judgment and does not apply to women taking birth control pills; one ovary is sufficient to diagnose PCO. The examination is more appropriate on the 3rd-5th day of the menstrual cycle or progesterone withdrawal bleeding . Ultrasound can help predict the outcome of clomiphene treatment, the occurrence of ovarian hyperstimulation syndrome and the timing of oocyte maturation in vivo. 4. Insulin resistance (IR): Insulin resistance (IR) refers to an insulin-mediated decrease in sugar utilization. The insulin resistance test is not necessary for the diagnosis of PCOS and does not affect the choice of treatment plan. Screening for metabolic syndrome should be done in obese patients, including oral glucose tolerance tests to screen for glucose intolerance. Further research is needed to determine whether to use these tests in non-obese patients, but additional risk factors (such as family history of diabetes) need to be considered when IR is present. 5, luteinizing hormone ( LH ): serum LH level measurement is not necessary for the clinical diagnosis of PCOS. However, LH has some value as a second-line parameter in lean patients or for research studies. PCOS is one of the most common causes of anovulatory infertility. Weight loss can reduce the concentration of insulin and androgens in the body and increase the concentration of sex hormone binding protein (SHBG) to help restore ovulation and normalize abnormal hormone levels. After 6 months of weight loss in obese patients, 55%-100% of patients regained ovulation after losing 5-10% of their body weight. Therefore, weight reduction has become the preferred method of treatment for obese patients. 2. Clomiphene: Nearly 80% of PCOS patients ovulate after taking clomiphene, but the pregnancy rate is only 35-40%. The high serum LH concentration is one of the reasons for the low response to clomiphene treatment. Secondly, the anti-estrogenic effect of clomiphene affects endometrial hyperplasia and cervical mucus properties, causing a contradiction between ovulation and pregnancy; and endometrial growth inhibition is heterogeneous independent of drug dose, with little possibility of pregnancy at endometrial thickness <8 mm. Adjuvant medication can improve treatment outcome: 5000-10000 IU of human chorionic gonadotropin (HCG) can avoid anovulation due to lack or delay of LH peak. 3. aromatase inhibitor (AI): Aromatase is a key enzyme in the conversion of androgens to estrogens. Aromatase inhibitors (AI) block estrogen synthesis by inhibiting the activity of this enzyme. Non-steroidal third-generation AI has the following characteristics that make it superior to conventional ovulation-promoting drugs (e.g., clomiphene) in ovulation-promoting treatment: (1) short half-life (45h), which can be rapidly cleared by the body without residual anti-estrogenic effects; (2) high specificity, no adverse effects on the endometrium, and no depletion of estrogen receptors despite the fact that estrogen levels are 2-3 times lower than clomiphene at ovulation, ensuring the endometrial response to The endometrium responds well to the high level of estrogen in the late follicular phase and can reach the thickness required for fertilized egg implantation at ovulation; (3) it has no adverse effect on the state of cervical mucus and is conducive to sperm passage. Foreign studies found that 12 PCOS patients who failed clomiphene treatment (10 cycles without ovulation, or endometrial thickness ≤5mm at the peak of LH) were treated with letrozole 2.5mg/d on the 3rd-7th day of menstruation for an average of 12 cycles, and the ovulation rate was 75% and 44%, and the pregnancy rate was 25% and 0%, respectively, compared with 18 cycles treated with clomiphene. It is clear that Letrozole can be used as a first-line ovulatory drug to compensate for the lack of clomiphene. 4. Gonadotropin therapy: The effect of progressive incremental gonadotropin therapy for PCOS is usually evaluated in terms of cumulative pregnancy rate. In polycystic ovaries (PCO), the FSH threshold is the same as in normal ovaries, but the number of follicles sensitive to low-dose FSH stimulation is twice as high as in normal ovaries. Once the FSH dose exceeds the PCO threshold, this results in multiple follicle development, leading to an increased risk of multiple pregnancies and ovarian transitional stimulation. In order to obtain a single dominant follicle, long-term low-dose stepwise FSH regimens designed according to the "threshold theory" strictly follow the principle of maintaining the required FSH dose for follicular development, but not exceeding it. The classic protocol is to start the cycle with 75 IU of FSH and increase by 37.5 IU at least every 7 days after 14 days as needed until follicle development begins. 5. Metformin: Hyperinsulinemia and IR can exacerbate endocrine and metabolic disorders in PCOS and aggravate a series of clinical manifestations such as hyperandrogenemia and anovulation, so it is important to reduce insulin concentration. Metformin can effectively reduce hyperglycemia in patients without causing the occurrence of hypoglycemia in normoglycemic individuals. The effectiveness of metformin has been confirmed by a large number of studies, that is, to reduce LH, blood insulin and serum androgen concentration, improve insulin sensitivity and blood SHBG concentration. the miscarriage rate of PCOS patients in the third trimester is as high as 30%-50%, and hyperinsulinemia is one of the important causes of miscarriage in early pregnancy. 6. In vitro fertilization-embryo transfer (IVF-ET): If the above methods are ineffective, IVF-ET can still achieve desirable results. In the study of Jiann-Loung, 1089 eggs were obtained in 60 cycles, 541 IVF and 548 ICSI (intracytoplasmic sperm injection) were performed, and the fertilization rate was 44.8±25.1: 72.3±15.5 The PCOS oocyte in vitro maturation (IVM) technique provides more opportunities for patients who need to undergo IVF. A French survey showed that 33 patients underwent 45 IVM cycles, 11 women were serum β-hCG positive (26.2% pregnancy rate in puncture cycles and 27.5% in transplant cycles), and 9 of them had clinical pregnancies (20.0% pregnancy rate in puncture cycles and 22.5% pregnancy rate in transplant cycles). No birth defects were detected in the born babies. However, the place of IVM in the management of PCOS needs to be clarified by additional randomized controlled trials. After PCOS patients are at an ideal weight, letrozole may be considered the drug of choice, and if ovulation failure or pregnancy does not occur, the following approaches are available: low-dose HMG therapy, metformin in combination with letrozole or HMG, and finally IVF-ET. regardless of the approach, few PCOS patients are currently infertile due to anovulation alone. More research and studies are needed to address the high rate of miscarriage and the high number of immature eggs at IVF in patients with PCOS.