Single sperm intracytoplasmic injection (ICSI): intracytoplasmic single sperm injection is a technique that uses microscopic manipulation techniques to inject a single sperm directly into the oocyte plasma to establish a pregnancy. Indications: 1. Severe oligospermia, hypospermia and teratospermia (must be confirmed by 3 or more tests.) 2. Irreversible obstructive azoospermia. 3, spermatogenic dysfunction (exclude genetic defects due to disease.) 4.Immune infertility. 5.In vitro fertilization failure. 6.Sperm acrosome abnormalities. 7. Pre-implantation embryo genetic testing is required. 8, Fertilization failure or very low fertilization rate in previous treatment cycles. 9, ICSI assisted fertilization is required after cryopreservation of eggs, or after immature eggs have matured in vitro. 10, Repeated IVF failure. Steps of ICSI: 1. Pre-treatment examination: Based on the routine IVF-ET preoperative examination, the male partner needs to check: FSH, LH, E2, PRL, T, karyotype; azoospermia patients need testicular or epididymal puncture to confirm the presence of viable sperm; if genetic factors are suspected to cause infertility, further relevant genetic examination should be performed. 2. Ovulation promotion and egg acquisition for the female partner are the same as for conventional IVF-ET. 3. Testicular or epididymal puncture is performed if necessary, and the procedure should be done by a urologist. 4. The obtained eggs are injected with intracytoplasmic single sperm. 5. Embryo transfer, luteal support and follow-up are the same as in conventional IVF-ET. There is no significant difference between the fertilization rate of IVF with normal semen and that of ICSI, but ICSI is an invasive treatment and should be limited to those who need it. ICSI has the potential to pass on genetic defects of oligo-, hypo-, and teratozoospermia to the next generation, and ICSI can lead to unknown damage to oocytes, so pregnancy after ICSI should be followed up intensively during pregnancy and postpartum.