Synchrony of the first division as an index of the blastocyst formation rate during embryonic development.

Purpose: To devise an uninvasive selection system for human embryos with high developmental potential after a single oocyte retrieval cycle by comparing the in vitro and in vivo effectiveness of first division synchrony against subsequent embryonic developmental stages. Methods: The effects of using assisted reproductive technology on 948 embryos that were produced in 137 cycles were examined by dividing the embryos into "early cleavage" (first division within 25.90 hours) and "late cleavage" (first division at or after 25.90 hours) groups and comparing the blastocysts and good-quality blastocyst formation rates between the two groups. These two groups were each divided further into "high synchrony" (first division synchrony within 3.96 hours) and "low synchrony" (first division synchrony at or after 3.96 hours) groups. The blastocysts, good-quality blastocyst formation rates, and pregnancy rates were compared among these four groups. Results: Both the blastocysts and good-quality blastocyst formation rates were significantly higher in the early-cleavage groups than in the late-cleavage groups. The blastocyst formation rate of the latter was also significantly increased in the high-synchrony, compared with the low-synchrony, group. Conclusion: First division synchrony in a single oocyte retrieval cycle could be a useful assessment of the blastocyst formation rate that enables the selection of viable embryos at an early stage of culture.

Selection of human blastocysts with a high implantation potential based on timely compaction.

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.

Developmental ability of embryos produced from oocytes with fragile oolemma by intracytoplasmic sperm injection.

PURPOSE: In intracytoplasmic sperm injection (ICSI) of oocytes with a fragile oolemma (fragile oocytes), breakage can occur at injection. In this study, we produced embryos from oocytes with a fragile and normal oolemma (normal oocytes) by ICSI and compared their ability to be fertilized and develop in vitro. We also investigated whether fragile oocyte-derived embryos could implant after blastocyst transfer to determine whether fragile oocytes should be used for assisted reproductive technology treatment. METHODS: Oocytes were divided into three groups-normal oocytes from cycles containing no fragile oocytes (group A), normal oocytes from cycles containing at least one fragile oocyte (group B), and fragile oocytes (group C), and their fertilization abilities after ICSI and the developmental abilities of resultant embryos were compared. RESULTS: The fertilization rate in group C (65.3 %) was significantly (P < 0.01) lower than those in groups A (84.6 %) and B (86.9 %), and the degeneration rate in group C (24.2 %) was significantly (P < 0.01) higher than those in groups A (0.71 %) and B (0.28 %). However, there were no significant differences in the blastocyst formation rates (59.7-67.5 %) of embryos among the different groups. In addition, the pregnancy rate after transfer of blastocysts in group C (50.0 %) was not significantly different from those in groups A (35.6 %) and B (45.8 %). CONCLUSIONS: The fertilization ability after ICSI of fragile oocytes is lower than that of normal oocytes but the resultant embryos have the same developmental ability as those of normal oocyte-derived embryos.

Effects of early cleavage patterns of human embryos on subsequent in vitro development and implantation.

OBJECTIVE: To establish a noninvasive selection system of human embryos with a high implantation potential before transferring. DESIGN: Cohort study. SETTING: Independent IVF clinics. PATIENT(S): One hundred sixty-four patients, with 791 embryos fertilized, checked, and recorded. INTERVENTION(S): Embryos were divided into nine groups according to the number of cells they contained and the extent of their fragmentation during the first and second divisions. We examined the effects of the cell division pattern and division time of embryos on subsequent development in vitro and in vivo using a time-lapse incubator. MAIN OUTCOME MEASURE(S): Rates of blastocyst formation, high-quality blastocyst formation, and pregnancy. RESULT(S): The rates of embryos developed into blastocysts and blastocysts in which both the inner cell mass and trophectoderm grades were scored B or higher (good-quality blastocysts) were high in groups that formed two cells during the first division and four cells during the second division, regardless of the presence or absence of fragmentation. In these groups the first and second division times (25.90 and 37.88 hours after culture, respectively) of embryos developed into good-quality blastocysts were significantly shorter than those of other embryos. Although embryo selection based on the first and second division times did not affect the pregnancy rates after transfer at day 2 or 3 of culture, it improved the pregnancy rates after blastocyst transfer at day 5. CONCLUSION(S): Transfer of blastocysts derived from embryos that completed first and second divisions within 25.90 and 37.88 hours after culture, respectively, brings about high pregnancy rates.