Sequential assessment of individually cultured human embryos as an indicator of subsequent good quality blastocyst development

BACKGROUND: It is of fundamental importance for IVF clinics to determine the most viable embryos for transfer. The challenge for ART clinics is to transfer fewer embryos, thereby minimizing the risk of multiple-infant births, while still maintaining the greatest chance of pregnancy for their patients. In this study, an investigation was made to determine if developmental markers on the day of fertilization (day 1) can predict good subsequent blastocyst development. METHODS AND RESULTS: A total of 1550 individually cultured 2PN embryos from 191 patients undergoing IVF/ICSI treatment at the Yale University Center for Reproductive Medicine and Infertility from February to December 2001 was included. The results showed a significant positive relationship between early-cleaving 2-cell embryos and subsequent good quality greater than or equal to4-cell, greater than or equal to7-cell and blastocyst development (P < 0.05). PN symmetry (the relative size of the PN to each other), when checked at the time fertilization, is also a significant indictor of good quality >= 4-cell, >= 7-cell stage embryos and blastocysts. Combined, a developing embryo showing PN symmetry with early cleavage and subsequent good >= 4-cell and >= 7-cell cleavage, has a one in two chance of developing into a good-quality blastocyst. CONCLUSION: Early embryo assessment can be used as an indicator of subsequent good blastocyst development.