Purpose: There is clinical evidence that early cleavage timing parameters predictive of blastocyst development also correlate with embryo implantation potential. The aim of this study is to determine the developmental competency of embryos with delayed blastulation.
Methods: Retrospective study performed from 2015 to 2016 at the Division of Reproductive Endocrinology and Infertility at Northwestern University.
Results: A total of 2,292 embryos from 524 patients were included. Day 6 blastocysts had statistically significant longer times for every time point analyzed than day 5 blastocysts (p < 0.001). We found no statistically significant difference in euploidy rates between day 5 (44%) and day 6 (41%) embryos (p = 0.573). t7 and t8 time points were independent predictors of euploidy after controlling for day of biopsy (p < 0.015 and p < 0.014, respectively). Intrauterine pregnancy (IUP) and live birth (LB) were less likely to occur after transferring day 6 embryos (p = 0.0033 and p = 0.0359) without previous genetic testing. However, in embryos that undergo preimplantation genetic testing for aneuploidy (PGT-A), there were no significant differences in IUP or LB rates.
Conclusion: Early time-lapse points can be used to predict embryo development. Day of blastulation may be an independent predictor IUP, with day 6 blastocysts having lower pregnancy and live birth rates. Our data suggests that day 5 and day 6 PGT-A tested embryos show similar rates of euploidy, suggesting that differences in PR seen in the non-PGT-A tested group may be caused by factors other than aneuploidy. Genetic testing technologies in combination with time-lapse microscopy may provide further information to improve IVF outcomes.
Keywords: Embryo development; Euploidy rates; IVF; Preimplantation genetic testing (PGT); Time-lapse morphology (TLM).