Optimization of a novel nylon mesh container for human embryo ultrarapid vitrification

Objective: To evaluate the efficacy of a nylon mesh container in vitrification of human embryos and to determine the optimal osmotic pressure of the initial thawing solution. Design: Retrospective analysis. Setting: National Center for Child Health and Development, Tokyo, Japan. Patient(s): Infertile patients undergoing either invitro fertilization or intracytoplasmic sperm injection in our hospital. Intervention(s): Embryos, at the cleavage stage, were cryopreserved using the vitrification method in either a plastic straw or a nylon mesh container. The embryos were thawed using an initial osmotic pressure of either 0.5 M or 1.0 M sucrose with subsequent step-wise dilution. After thawing, the embryos were transferred to the uterus. Main Outcome Measure(s): Survival rate of blastomeres, embryo survival rate, implantation, and pregnancy rates, cancellation rate because of embryo damage. Result(s): Use of nylon mesh and the 1.0 M sucrose thawing solution significantly improved blastomere survival rate (98.0 +/- 1.0%, mean +/- SEM), pregnancy rate (41.0%) and implantation rate (32.3%). Conclusion(s): Vitrification using a nylon mesh container and subsequent thawing in a 1.0 M sucrose solution is an easy and inexpensive method that improves the reliability of embryo cryopreservation of embryos without adverse effects on clinical outcomes. (Fertil Steril (R) 2010; 93: 2405-10. (C)2010 by American Society for Reproductive Medicine.)