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.