Effect of Vitrification Procedure on Chromosomal Status of Embryos Achieved from Vitrified and Fresh Oocytes (Report‪)‬

1. INTRODUCTION Human oocytes cryopreservation is an attractive choice to the range of fertility treatments presently offered. Since the very first frozen oocyte pregnancy was achieved in humans by Chen [1], the slow cooling method has been applied with varying success [2-7]. There are many reports about the cryopreservation of human oocytes with good fertilization and cleavage rates [1,8] but with variable results on pregnancy rates per cycle [9-13]. A recent meta-analysis on slow freezing revealed that the clinical pregnancy rate per transfer with this method was 20.6%, and 2.3% per thawed oocyte [14].