Quantitative grading of a human blastocyst: optimal inner cell mass size and shape

Objective: To investigate the predictive value of quantitative measurements of blastocyst morphology on subsequent implantation rates after transfer. Design: Prospective observational study. Setting: Private assisted reproductive technology center. Patient(s): One hundred seventy-four IVF patients receiving transfers of ex panded blastocyst-stage embryos on day 5 (n = 112) or day 6 (n = 62) after oocyte retrieval. Intervention(s): None. Main Outcome Measure(s): Blastocyst diameter, number of trophectoderm cells , inner cell mass (ICM) size, ICM shape, and implantation and pregnancy rat es. Result(s): Blastocyst diameter and trophectoderm cell numbers were unrelate d to implantation rates. Day 5 expanded blastocysts with ICMs of >4,500 mum (2) implanted at a higher rate than did those with smaller ICMs (55% vs. 31 %). Day 5 expanded blastocysts with slightly oval ICMs implanted at a highe r rate (58%) compared with those with either rounder ICMs (7%) or more elon gated ICMs (33%). Implantation rates were highest (71%) for embryos with bo th optimal ICM size and shape. Pregnancy rates were higher for day 5 transf ers of optimally shaped ICMs compared with day 5 transfers of optimally siz ed ICMs. Conclusion(s): Quantitative measurements of the inner cell mass are highly indicative of blastocyst implantation potential. Blastocysts with relativel y large and/or slightly oval ICMs are more likely to implant than other bla stocysts. (Fertil Steril (R) 2001;76:1157-67. (C) 2001 by American Society for Reproductive Medicine.).