Microstimulation protocols, also known as mild stimulation protocols, are characterized by low ovarian stimulation, short course of treatment, safety and convenience, which is a trend in recent years in IVF treatment at home and abroad. Microstimulation protocol is to promote follicle growth by applying small doses of ovulation-promoting drugs, including oral ovulation-promoting drugs alone or small doses of ovulation-promoting injections, or a combination of both, with the dose of injections generally not exceeding 150u/day. The microstimulation protocol does not have a descending regulation process. Ovulation treatment starts on the 3rd-5th day of menstruation and the course of treatment is usually about 8-10 days, after the follicles have grown to 17-18mm in diameter, chorionic gonadotropin (HCG) is given as an overnight injection and the eggs are retrieved 36 hours after the overnight injection. Compared with the general long protocol, the microstimulation regimen has a shorter ovulation treatment cycle, a smaller total dose of ovulation-promoting drugs, less costly treatment, less stimulation of the ovaries, less prone to complications such as ovarian hyperstimulation, and less risky, but, accordingly, the microstimulation regimen generally has a lower number of eggs obtained and fewer embryos can be transferred. At present, the main clinical application of microstimulation is for older patients with declining ovarian function and low ovarian response to conventional IVF regimens, and also for patients with polycystic ovary syndrome and severe ovarian hyperstimulation syndrome in the past. Microstimulation protocols for patients With the gradual improvement and diversification of IVF treatment protocols, the concept of “individualized treatment” is gradually accepted by doctors and patients. At present, microstimulation is mainly used for patients with the following conditions: firstly, patients with declining ovarian function. Due to old age or prematurely declining ovarian function, the number of basal sinus follicles in both ovaries is low and the ovarian response to conventional ovulation regimens is low, and increasing the dose of ovulatory drugs cannot increase the number of eggs obtained nor improve egg quality. In contrast, the use of microstimulation allows for the development of follicles that are more sensitive to the drug, and although the number of mature eggs obtained is low, the quality of the eggs is higher, and there are data proving that for this population, the chances of obtaining normal embryos with microstimulation treatment are higher than with conventional regimens. At the same time, the short cycle of ovulation treatment with microstimulation can increase the number of normal embryos obtained by increasing the number of ovulation cycles, thus increasing the pregnancy rate. Secondly, patients with polycystic ovary syndrome (PCOS). Polycystic ovary syndrome is characterized by high number of eggs obtained, high number of embryos available for transfer, hyperstimulation of the ovaries, etc. It is prone to ovarian hyperstimulation syndrome, ascites, pleural fluid, hemoconcentration, abnormal liver and kidney function, and the high rate of fresh cycle cancellation transfer is valued by doctors and patients. In recent years, microstimulation protocols have been advocated for patients with polycystic ovary syndrome, applying small doses of ovulation-promoting drugs to control ovarian response and reduce the number of eggs obtained, thus reducing the risk of ovarian hyperstimulation syndrome, in order to increase the chance of fresh cycle transplantation, reduce medical costs, and increase the rate of fresh cycle pregnancy in patients. Thirdly, microstimulation is also a safe treatment for some patients with high risk of ovarian tumor and those who have fertility requirements after previous ovarian tumor surgery. In conclusion, microstimulation is gentle and flexible, with a short course of treatment, low cost, and little ovarian hyperstimulation, but the number of eggs obtained and the number of embryos that can be transferred is low, so the clinician needs to fully communicate with the patient after a thorough assessment of her condition and adopt an individualized treatment plan according to her specific situation. The main drugs used in the microstimulation program include: clomiphene, letrozole, urotropin, etc. From the 3rd to 5th day of menstruation, vaginal ultrasound and hormone monitoring will be performed. The eggs were retrieved 36 hours after the night injection. In general, microstimulation does not have a descending regulation process, so it is easy to have early LH peaks and early ovulation. Therefore, serum hormone values need to be monitored closely during ovulation promotion, and if there is any abnormality, eggs should be retrieved earlier. If clomiphene is applied in the early stage of ovulation promotion, due to the effect of clomiphene on the endometrium, it is generally recommended to freeze the whole embryo and then prepare the endometrium for freezing and recovery cycle transfer after menstruation.