Successful pregnancies and deliveries after a simple vitrification protocol for day 3 human embryos

Objective: To evaluate the efficacy and efficiency of freezing cleaved human embryos through vitrification. Design: Clinical study of vitrification of human embryos. Setting: Assisted reproductive technology centers. Patient(s): Thirty-six patients undergoing IVF-ICSI treatment whose surplus embryos were frozen. Intervention(s): Two hundred fifteen surplus embryos vitrified, subsequently thawed, and transferred in natural or controlled cycles. Main Outcome Measure(s): Embryo survival rate after thawing and resultant patient pregnancy rate. Result(s): From the 215 vitrified and thawed embryos, 106 survived, with an overall embryo survival rate of 49.3%. The survival rate was higher when embryos were vitrified at the eight-cell stage compared with at the six to seven-cell and six-cell stages (79.2%, 39.7%, and 21.1%, respectively). On average, 2.9 +/- 1.2 embryos per patient were transferred, resulting in 11 pregnancies (30.5%), with an implantation rate of 10.4% per embryo transferred. Conclusion(s): Ultrarapid embryo freezing by vitrification of eight-cell stage embryos is a reliable method, as evidenced by high rates of embryo survival and pregnancy, making it a superior alternative to the conventional slow-cooling method. (C) 2001 by American Society for Reproductive Medicine.