Human Reproduction, Vol. 16, No. 9, 1970-1975,
September 2001
© 2001 European Society of Human Reproduction and Embryology
The Graduated Embryo Score (GES) predicts blastocyst formation and pregnancy rate from cleavage-stage embryos*
1 Sher Institute for Reproductive Medicine, Las Vegas, Nevada, USA and 2 Department of Obstetrics and Gynecology, University of Nevada School of Medicine, Reno, Nevada, USA
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 potentially 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 alignment along the pronuclear axis, regular cleavage and degree of fragmentation at the first cell division, and cell number and morphology on day 3 were weighted to create a possible GES of 100 for each of 1245 fertilized embryos derived from 109 patients aged <40 years. The GES was correlated with IVF outcome. RESULTS: Of 983 embryos for extended culture, 349 (36%) developed to blastocyst and 180 (18%) were good quality (grade I–II). When ranked by cell number and morphology alone, 34% of embryos with 
7 cells and <20% fragmentation formed good quality blastocysts. Using GES, embryos scoring 90–100 had 64% blastocyst formation compared with 31% scoring 70–85 and with 11% scoring 30–65. Embryos scoring 70–100 had 44% blastocyst development compared with 9% scoring 0–65. Fifty-six patients (51%) conceived on-going gestations from 294 transferred embryos. In patients with at least one transferred embryo scoring 70, the pregnancy rate was 59% compared with 34% if all embryos scored <70. The overall implantation rate was 28%. Among embryos scoring 70–100, an implantation rate of 39% was seen, compared with 24% among embryos scoring 0–65. CONCLUSIONS: Predicting which cleaved embryos will form blastocysts could permit the high success rates associated with blastocyst transfer to be achieved from day 3 embryo transfer.
Key words: blastocyst development/graduated embryo scoring/implantation/IVF
3 To whom correspondence should be addressed at: 3121 S.Maryland Parkway, Suite 300, Las Vegas, NV 89109 USA.E-mail: jfisch{at}sherinstitute.com
* Presented in part at the 56th Annual meeting of the American Society for Reproductive Medicine, San Diego, CA, USA October 21-26, 2000.
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