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

ObjectiveTo describe success rates with bipronuclear (2PN) oocyte cryopreservation, followed by thaw, extended culture, and blastocyst transfer.DesignRetrospective study.SettingPrivate 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.