Predictive value of 72-hour blastomere cell number on blastocyst development and success of subsequent transfer based on the degree of blastocyst development

Objective: To determine the predictive value of 72-hour blastomere cell num ber on blastocyst development and to compare success rates of subsequent tr ansfer based on the degree of blastocyst development. Design: Retrospective clinical study. Setting: Private assisted reproductive technology center. Patient(s): Ninety-three women aged 32.0 +/- 5.1 years undergoing oocyte re trieval for NF. Intervention(s): Bipronueleate oocytes obtained from IVF were grown for up to 168 hours after fertilization and subsequently transferred at the blasto cyst stage. Main Outcome Measure(s): Percentages of embryos developing to blastocyst fr om 72-hour embryos by blastomere cell number and subsequent implantation an d pregnancy rates of transferred blastocysts. Result(s): Rates of blastocyst formation and expansion increased as cell nu mbers at 72 hours increased. implantation rates were 43% for embryos transf erred to women receiving only expanded blastocysts and 17% for embryos tran sferred to women receiving one or more less developed blastocysts. Pregnanc y rates were higher for women receiving only expanded blastocysts than for women receiving one or more less developed blastocysts, although the differ ence was not significant. Conclusion(s): More developed 72-hour embryos are more likely to become bla stocysts and expand, implantation rates are greater for the transfer of exp anded rather than unexpanded blastocysts. (C) 2000 by American Society for Reproductive Medicine.