Live births after vitrification of oocytes in a stimulated in vitro fertilization-embryo transfer program.

OBJECTIVE To assess the usefulness of the vitrification method in clinical practice. DESIGN Clinical study of vitrification of human oocytes. SETTING A university-affiliated hospital. PATIENT(S) Thirty-four patients who agreed to undergo additional IVF-ET after the failed fresh cycle using the previously vitrified/thawed oocytes. INTERVENTION(S) Surplus oocytes from the IVF-ET patients were vitrified for the next cycle. MAIN OUTCOME MEASURES Morphologic normality of post-thawed oocytes, fertilization, cleavage, pregnancy, and implantation rate. RESULT(S) Overall morphological survival and fertilization rates of vitrified/liquefied oocytes were 68.6% (325/474) and 71.7% (142/198), respectively. Pregnancy rate and implantation rate per embryo transfer were 21.4% (6/28) and 6.4% (8/125), respectively. All pregnancies resulted in the delivery of healthy babies (1 twin and 5 singletons/6 pregnancies). CONCLUSION(S) The feasibility of the vitrification method for human oocytes was confirmed by our clinical results. Subsequent studies on vitrification and thawing procedures should be undertaken for further optimizing the vitrification method.