The efficiency of oocyte vitrification for donor oocyte cycles and oocyte banking in ART

Abstract

OBJECTIVE: Vitrification is proving to be a highly efficient method for oocyte cryopreservation. Fertilization, embryo development and clinical outcome from vitrified oocytes have been shown to be comparable to results achieved with fresh oocytes. This study analyzed the efficiency of vitrification techniques for both donor oocyte cycles and oocyte banking in a human ART program. DESIGN: Retrospective study. MATERIALS AND METHODS: The study population consisted of Group A = 14 oocyte donors (mean maternal age = 28.9 years) and Group B = 25 patients presenting for ooycte banking (mean maternal age = 34.8 years). Reasons for oocyte banking included no sperm, uterine anomaly or ovarian hyperstimulation risk. Following controlled ovarian hyperstimulation, a total of 533 mature oocytes (Group A=219 and Group B=314) were vitrified using the Cryotop method. An embryo transfer was scheduled after endometrial preparation. RESULTS: Following warming, a total of 451 oocytes survived the vitrification process; Group A=195 (89.04%) and Group B=256 (81.53%) (P<0.05). Comparable fertilization (Group A=79.38% and Group B=78.52%) and cleavage rates (Group A=89.61% and Group B=89.06%) were observed between the groups. In addition, implantation (Group A=44.83% and Group B=40.98%) and clinical pregnancy (Group A=64.29% and Group B=58.33%) rates were also not significantly different. In relation to the day of transfer, Group A consisted of n=8 D3 and n=6 D5 embryo transfers, while Group B included a higher proportion of D3 embryo transfers (n=15; 62.5%) (ns). Only one patient in Group B did not receive a transfer due to no oocytes surviving. CONCLUSION: Vitrification of oocytes using the Crytop method results in excellent clinical outcome including survival post warming, fertilization, cleavage and pregnancy rates. This procedure represents a viable option for women participating in donor oocyte programs, healthy women requesting oocyte banking and fertility preservation for indicated cancer patients prior to chemotherapy treatment.