57 Zu dieser Frage ausführlich DENNY SAKKAS/DAVID K. GARDNER, Evaluation of embryo quality: sequential analysis of embryo development with the aim of single embryo transfer, in: D. K. Gardner/A. Weissmann/C. M. Howles/Z. Shoham (Hrsg.), Textbook of Assisted Reproductive Techniques, London 2004, S. 235 ff. VPB/JAAC/GAAC 2008 217 Gutachten