Clomiphene, a very classic old drug, is a first-line drug, which is used from the 3rd-5th day of menstruation, with an initial dose of 50mg, to combine with the estrogen receptors of the hypothalamus and pituitary gland to stimulate the hypothalamus pituitary gland to produce more FSH and LH to stimulate follicle development, but because clomiphene has anti-estrogenic effects, the endothelium will be relatively However, because of the anti-estrogenic effect of clomiphene, the endothelium is relatively thin and there is no negative feedback regulation of estrogen, so the level of follicular estrogen will be higher; 2. Letrozole, a new drug, is an aromatase inhibitor, which is a second-line drug, initially used for the treatment of breast cancer, its usage is similar to clomiphene, also starting from 3-5 days of menstruation, the initial dose is 2.5-7.5mg, but now there are some experts and guidelines recommend it for However, some experts and guidelines now recommend it as the first-line drug for patients with polycystic ovary syndrome, especially for obese patients with polycystic ovary syndrome, and its egg and embryo acquisition rates for individual follicles are better than those of clomiphene; 3. Patients with low gonadotropins generally use HMG directly.