Purpose: Recently, we established a noninvasive system for selecting human blastocysts with a high pre-transfer implantation potential based on first and second division patterns. The present study was carried out to improve the selection system.
Methods: Embryos that completed first and second divisions within 25.90 and 37.88 h after culture, respectively, were selected using a time-lapse incubator. We examined the effects of compaction and blastocyst formation times on pregnancy rates after transferring these embryos at the blastocyst stage.
Results: The completion of compaction and blastocyst formation times (79.93 and 97.47 h after culture, respectively) of embryos resulting in pregnancies after transfer were significantly (P < 0.01) shorter than those (86.46 and 100.34 h after culture, respectively) of embryos that failed to induce pregnancies. Embryo selection based on completion of compaction time improved pregnancy rates (40.9 vs. 74.6%, P < 0.01).
Conclusions: Of the embryos that formed two cells during the first division within 25.90 h after culture and four cells during the second division within 37.88 h after culture, those that completed compaction within 79.93 h after culture before reaching the blastocyst stage had a high implantation potential.
Keywords: Compaction; Morula; Single blastocyst transfer; Time-lapse incubator.