endometrial receptivity, high body mass index, in vitro fertilization/intracytoplasmic sperm injection, modified ultra-long protocol, pregnancy outcome, Immunologic diseases. Allergy, RC581-607, Diseases of the endocrine glands. Clinical endocrinology, RC648-665

Objective: Overweight and obesity are increasingly epidemic and negatively related to reproductive outcome. The aim of this study was to investigate the advantages of a modified ultra-long downregulation protocol on pregnancy outcomes of patients with high body mass index (BMI) undergoing in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI), compared to the long protocol (LP). Methods: We retrospectively analyzed the clinical data of 3,920 infertile patients at the Reproductive and Genetic Hospital of Citic-Xiangya from January 2012 to December 2017 by propensity score matching (PSM). Patients were divided into two groups: modified ultra-LP (MULP) (n = 1,960) and LP (n = 1,960). Results: In the MULP group, live birth rate (52.65% vs. 46.79%,P < 0.001, odds ratio [OR]: 1.784, 95% confidence interval [CI]: 1.563–2.036), clinical pregnancy rate (62.50% vs. 57.91%, P = 0.003, OR: 1.211, 95% CI: 1.066–1.377), and implantation rate (53.24% vs. 49.65%, P = 0.004, OR: 1.155, 95% CI: 1.048–1.272) were statistically significantly higher than those of the LP group. Moreover, the cycle cancellation rates (12.70% vs. 15.15%, P = 0.027, OR: 0.815, 95% CI: 0.68–0.977), abortion rates (12% vs. 14.8%, P = 0.046, OR: 0.785, 95% CI: 0.619–0.996), and ectopic pregnancy rates (1.06% vs. 2.11%, P = 0.04, OR: 0.497, 95% CI: 0.252–0.98) were lower than those in the LP group. Conclusion: The modified ultra-long downregulation protocol improved the pregnancy outcomes in patients with high BMI undergoing IVF/ICSI treatment, providing a potential option for physicians when deciding an optimized ovary stimulation protocol for high BMI patients.