Abstract
PURPOSE: To report on successful birth after the transfer of postthawed human zygotes that were vitrified using a conventional straw for the purpose of protecting them from infections and a low-toxicity cryoprotectant that is commercially sold. METHODS: A primary infertile couple presented at our IVF program. After being checked for fertilization, the embryos were not transferred to the uterus at that cycle. Instead, all of them were cryopreserved at the 2-pronuclei stage using our original vitrification method. After the vitrification and warming of four zygotes, two embryos were transferred into the uterus. RESULTS: Twenty-one 2-pronuclei embryos were vitrified in liquid nitrogen. After 2 embryos were thawed and transferred, successful pregnancy was the outcome, and a healthy boy was born at term. CONCLUSIONS: Vitrification is a simple procedure and requires less time than slow freezing. Vitrification of zygotes in a conventional straw seems to be sufficient for viability and works to store the zygotes safely.