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Updated: Jun 28, 2026
Cryopreservation of Preimplantation Embryos of Cattle, Sheep, and Goats
Published on: August 5, 2011
High ongoing pregnancy rates after deferred transfer through bipronuclear oocyte cryopreservation and post-thaw
Bruce S Shapiro1, Said T Daneshmand, Forest C Garner
1Fertility Center of Las Vegas, University of Nevada School of Medicine, Las Vegas, Nevada 89117, USA. bsshapiro@aol.com
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.
