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 in vitro 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.