High ongoing pregnancy rates after deferred transfer through bipronuclear oocyte cryopreservation and post-thaw extended culture

Objective: To describe success rates with bipronuclear (2PN) oocyte cryopreservation, followed by thaw, extended culture, and blastocyst transfer. Design: Retrospective study. Setting: Private fertility center. Patient(s): There were 48 blastocyst transfers after post-thaw extended culture in patients less than 35 years old and 43 transfers in patients 35-40 years old. Intervention(s): Patients opted for cryopreservation of their entire cohorts at the 2PN stage. Thawed 2PN oocytes were cultured to the blastocyst stage before transfer. Main Outcome Measure(s): Implantation, ongoing pregnancy. Result(s): Among patients less than 35 years old at oocyte retrieval, there were 59 thaws of 2PN oocytes, 48 blastocyst transfers, and 40 ongoing pregnancies (79.2% per transfer), the implantation rate was 64.2%, and the ongoing pregnancy rate (PR) per thaw was 64.4%. Among patients 35-40 years of age at retrieval, there were 58 thaws, 43 blastocyst transfers, and 22 ongoing pregnancies (51.2% per transfer), the implantation rate was 44.0%, and the ongoing PR per thaw was 39.3%. Patients less than 35 years old had significantly greater rates of implantation and ongoing pregnancy than did patients 35-40 years of age. Patients with 12 or more 2PN oocytes had significantly greater rate of ongoing pregnancy than those with fewer than 12 2PN oocytes. Conclusion(s): Post-thaw extended culture and blastocyst transfer yield high rates of implantation and ongoing pregnancy. Ongoing PRs decline with increasing age. (Fertil Steril (R) 2009;92:1594-9. (C) 2009 by American Society for Reproductive Medicine.)