Delayed blastulation, multinucleation, and expansion grade are independently associated with live-birth rates in frozen blastocyst transfer cycles

Objective: To identify blastocyst features independently predictive of successful pregnancy and live births with vitrified-warmed blastocysts. Design: Retrospective study. Setting: Academic hospital. Patient(s): Women undergoing a cycle with transfer of blastocysts vitrified using the Rapid-i closed carrier (n = 358). Intervention(s): None. Main Outcome Measure(s): Clinical pregnancy and live-birth rates analyzed using logistic regression analysis. Result(s): A total of 669 vitrified-warmed blastocysts were assessed. The survival rate was 95%. A mean of 1.7 +/- 0.5 embryos were transferred. The clinical pregnancy, live-birth, and implantation rates were 55%, 46%, and 43%, respectively. The odds of clinical pregnancy (odds ratio [OR] 3.08; 95% confidence interval [CI], 1.88-5.12) and live birth (OR 2.93; 95% CI, 1.79-4.85) were three times higher with day-5 blastocysts versus slower-growing day-6 vitrified blastocysts, irrespective of patient age at cryopreservation. Blastocysts from multinucleated embryos were half as likely to result in a live birth (OR 0.46; 95% CI, 0.22-0.91). A four -fold increase in live birth was observed if an expanded blastocyst was available for transfer. The inner cell mass-trophectoderm score correlated to positive outcomes in the univariate analysis. The implantation rate was statistically significantly higher for day-5 versus day-6 vitrified blastocysts (50% vs. 29%, respectively). Conclusion(s): The blastocyst expansion grade after warming was predictive of successful outcomes independent of the inner cell mass or trophectoderm score. Delayed blastulation and multinucleation were independently associated with lower live-birth rates in frozen cycles. Implantation potential of the frozen blastocysts available should be included in the decision-making process regarding embryo number for transfer. (C) 2016 The Authors. Published by Elsevier Inc. on behalf of the American Society for Reproductive Medicine.