Objective: To investigate the clinical effects of oocyte cryopreservation in assisted reproduction technology (ART).
Methods: 258 patients undergoing retrieval of more than 20 oocytes during in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) were divided into 2 groups:Group A, undergoing surplus oocytes cryopreservation (84 cycles) and Group B undergoing embryo cryopreservation (174 cycles) according to the patients' choices. Fertilization rate and clinical pregnancy rate of fresh embryo transfer cycle were compared between these two groups. Twenty-three infertile couples' frozen oocytes were thawed for further ART treatment. Among them, fifteen couples received embryo transfer using their own frozen-thawed oocytes, and other four couples used donated frozen-thawed oocytes. The survival rate, fertilization rate, cleavage rate, implantation rate, and clinical pregnancy rate of these 19 cycles were compared to the outcome of 56 frozen-thawed embryo transfer cycles.
Results: The fertilization rate of Group A who underwent IVF was 65.9%, not significantly different from that of Group B who received IVF (66.9%, P > 0.05), and the fertilization rate of Group A who underwent ICSI was 71.6%, not significantly different from that of Group B who received ICSI (64.1%, P > 0.05). The clinical pregnancy rate (per embryo transfer cycle) of Group A who received IVF was 52.9%, not significantly different from that of Group B who received IVF (42.3%, P > 0.05), and the clinical pregnancy rate (per embryo transfer cycle) of Group A who received ICSI was 35.5%, not significantly different from that of Group B who received ICSI (34.4%, P > 0.05). The clinical pregnancy rate of frozen-thawed oocyte group (per embryo transfer cycle) was 47.4% (9/19). Four couples used donated frozen-thawed oocytes, two of them got clinical pregnancy and one of them had term delivery.
Conclusion: For women who undergo retrieval of more than 20 oocytes in IVF/ICSI, the clinical outcome of fresh embryo transfer cycle, such as fertilization rate and clinical pregnancy rate, are not influenced by oocyte cryopreservation and embryo cryopreservation. There is no significant difference in the clinical pregnancy rate (per embryo transfer cycle) between frozen-thawed oocyte group and frozen-thawed embryo group. Compared with embryo cryopreservation, oocyte cryopreservation has obvious advantages in fertility preservation and oocyte donation.