The Graduated Embryo Score (GES) predicts blastocyst formation and pregnancy rate from cleavage-stage embryos

BACKGROUND: Embryo morphology and cleavage rates alone do not consistently identify embryos with high implantation potential following IVF. Blastocyst transfer has been reported to improve success rates by identifying potenti ally superior quality embryos. Algorithms for predicting IVF outcomes based on the presence of early developmental milestones have been proposed. Here we introduce the Graduated Embryo Score (GES). METHODS: Nucleolar alignmen t along the pronuclear axis, regular cleavage and degree of fragmentation a t the first cell division, and cell number and morphology on day 3 were wei ghted to create a possible GES of 100 for each of 1245 fertilized embryos d erived from 109 patients aged <40 years. The GES was correlated with IVF ou tcome. RESULTS: Of 983 embryos for extended culture, 349 (36%) developed to blastocyst and 180 (18%) were good quality (grade I-II). When ranked by ce ll number and morphology alone, 34% of embryos with <greater than or equal to>7 cells and <20% fragmentation formed good quality blastocysts. Using GE S, embryos scoring 90-100 had 64% blastocyst formation compared with 31% sc oring 70-85 and with 11% scoring 30-65. Embryos scoring 70-100 had 44% blas tocyst development compared with 9% scoring 0-65. Fifty-six patients (51%) conceived on-going gestations from 294 transferred embryos. In patients wit h at least one transferred embryo scoring <greater than or equal to>70, the pregnancy rate was 59% compared with 34% if all embryos scored <70. The ov erall implantation rate was 28%. Among embryos scoring 70-100, an implantat ion rate of 39% was seen, compared with 24% among embryos scoring 0-65. CON CLUSIONS: Predicting which cleaved embryos will form blastocysts could perm it the high success rates associated with blastocyst transfer to be achieve d from day 3 embryo transfer.