〔Abstract〕 Objective To investigate the influence of prior cesarean section on the pregnancy, delivery and neonatal outcomes ofin vitrofertilization and embryo transfer. Methods 235 patients with prior cesarean section were collected from the assisted reproductive center, and their clinical information were retrospectively analyzed. Patients were divided into two groups according to the previous cesarean scar defect(PCSD) with 158 cases in NPCSD group and 77 cases in PCSD group. The control group consisted of 219 patients who had only previous vaginal delivery in the same period. The basic data, pregnancy, delivery and neonatal outcomes were compared among the three groups of patients. Results The basic data, Gn duration, Gn dosage, estradiol(E2) level on human chorionic gonadotrophin(hCG) injection day, mean number of retrieved oocytes, number of high-quality embryo, endometrial thickness on ovulation day and number of transfer embryos were similar between previous cesarean section group and previous vaginal delivery group. The embryo implantation rate, clinical pregnancy rate and take-home baby rate were significantly lower in PCSD group than NPCSD group and previous vaginal delivery group(P<0.05). Twin deliveries had lower gestational age and neonatal birth weight compared with singleton deliveries in previous cesarean section group and previous vaginal delivery group. Twin deliveries had higher preterm birth rate compared with singleton deliveries in both groups(P<0.05). Conclusion From the clinical data, it should be the cesarean scar defect rather than the previous cesarean history that causes significant decrease of implantation rate, clinical pregnancy rate and take-home baby rate. But it does not affect abortion rate and neonatal outcomes. And it is an important factor affecting the outcome of assisted reproductive technology. It should reduce the number of transfer embryos to control multiple pregnancy in patients with previous cesarean section.