Thomas J. Kim

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.

Vitrification of oocytes produces high pregnancy rates when carried out in fertile women

OBJECTIVE To determine the efficiency of our vitrification technique when applied in young fertile women. DESIGN Clinical research and application. SETTING In vitro fertilization center. PATIENT(S) Twenty-one women were recruited from the navy community with 19 patients finishing the study. INTERVENTION(S) Vitrified oocytes with use of the electron microscopic grid method were warmed 6 months after vitrification. Surviving metaphase II oocytes were microinjected for fertilization, and clinical results were evaluated. MAIN OUTCOME MEASURE(S) Survival, fertilization, and cleavage rate. Pregnancy and implantation rate. RESULT(S) Three hundred ninety-five oocytes were warmed, of which 320 oocytes (81.0%) survived. Two hundred eighty-five metaphase II oocytes were microinjected for fertilization; 206 of them (72.3%) fertilized, and 53 embryos were transferred to 19 patients (in 20 warming cycles). Twenty-four of 53 transferred embryos (45.3%) implanted as confirmed by ultrasound examination. Of the 20 transfers, 16 resulted in clinical pregnancy (80%), 3 miscarried (15%), and 13 (65%) went on to produce 20 live births, respectively. This is much higher in comparison with our previous data using supernumerary oocytes where the rates of implantation and pregnancy were 6% and 21%. Live-birth rates per warmed oocyte and per injected oocyte were 5.1% and 7.2%, respectively. CONCLUSION(S) High pregnancy and implantation rates were observed after 6 months of cryopreservation by vitrification when oocytes from fertile woman were used. Proper screening of candidates for oocyte cryopreservation is of crucial importance to assure a favorable pregnancy outcome.

Cryopreserved human blastocysts after vitrification result in excellent implantation and clinical pregnancy rates

We conducted a retrospective review of all frozen ETs from May 2002 to October 2007 using our new vitrification technique in order to determine its efficacy. We found high pregnancy (70.5%; 79/112) and implantation (40.6%; 110/271) rates with the use of this new method.