Hum. Reprod. Advance Access originally published online on June 7, 2008
Human Reproduction 2008 23(9):1983-1992; doi:10.1093/humrep/den206
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Quantitative morphometrical characterization of human pronuclear zygotes
1 Biomedical Imaging Group, Swiss Federal Institute of Technology Lausanne, Lausanne, Switzerland 2 Women’s General Hospital, IVF-Unit, Linz, Austria 3 Fondation F.A.B.E.R & Centre of Medically Assisted Procreation, Lausanne, Switzerland 4 Department of Electronic and Telecommunication Systems, University of San Pablo — CEU, Campus Urb. Montepríncipe s/n, 28668 Boadilla del Monte, Madrid, Spain
5 Correspondence address. E-mail: coss.eps{at}ceu.es
BACKGROUND: Identification of embryos with high implantation potential remains a challenge in in vitro fertilization (IVF). Subjective pronuclear (PN) zygote scoring systems have been developed for that purpose. The aim of this work was to provide a software tool that enables objective measuring of morphological characteristics of the human PN zygote.
METHODS: A computer program was created to analyse zygote images semi-automatically, providing precise morphological measurements. The accuracy of this approach was first validated by comparing zygotes from two different IVF centres with computer-assisted measurements or subjective scoring. Computer-assisted measurement and subjective scoring were then compared for their ability to classify zygotes with high and low implantation probability by using a linear discriminant analysis.
RESULTS: Zygote images coming from the two IVF centres were analysed with the software, resulting in a series of precise measurements of 24 variables. Using subjective scoring, the cytoplasmic halo was the only feature which was significantly different between the two IVF centres. Computer-assisted measurements revealed significant differences between centres in PN centring, PN proximity, cytoplasmic halo and features related to nucleolar precursor bodies distribution. The zygote classification error achieved with the computer-assisted measurements (0.363) was slightly inferior to that of the subjective ones (0.393).
CONCLUSIONS: A precise and objective characterization of the morphology of human PN zygotes can be achieved by the use of an advanced image analysis tool. This computer-assisted analysis allows for a better morphological characterization of human zygotes and can be used for classification.
Key words: zygote/in vitro fertilization/image analysis/morphometrical characterization
Submitted on November 9, 2007; resubmitted on February 7, 2008; accepted on March 21, 2008.