Long-term Cryopreservation of Human Oocytes Does Not Increase Embryonic Aneuploidy

Objective: To determine if long-term cryopreservation of human oocytes affects oocyte developmental competence, blastocyst euploidy, or live-birth rates.

Design: Retrospective cohort study.

Setting: University-based fertility center.

Patient(s): A total of 33 patients with cryopreserved oocytes underwent oocyte thaw, blastocyst culture, trophectoderm biopsy, and 24-chromosome preimplantation genetic screening (PGS) with array comparative genomic hybridization between December 2011 and July 2014; subjects were compared with 2:1 age-matched controls with fresh oocytes whose embryos underwent trophectoderm biopsy and PGS during the same period.

Intervention(s): None.

Main Outcome Measure(s): Rates of fertilization, blastulation, euploidy, implantation, and live birth.

Result(s): Thirty-three patients (mean age 36.2 ± 3.8 y) thawed 475 oocytes that had been cryopreserved for a median of 3.5 years. Compared with 66 age-matched controls who underwent in vitro fertilization and PGS with fresh oocytes, embryos derived from cryopreserved oocytes demonstrated compromised blastocyst formation (54.5% vs. 66.2%) despite no impairment in fertilization (72.8% vs. 73.2%). Results showed no difference in the number of euploid blastocysts (1.7 ± 1.9 vs. 2 ± 2.5), percentage of euploid blastocysts (44.5% vs. 47.6%), rate of implantation (65% vs. 65%), or rate of live birth and ongoing pregnancy (62.5% vs. 55%) after 24-chromosome PGS with cryopreserved or fresh oocytes.

Conclusion(s): Embryos derived from cryopreserved oocytes demonstrate impaired blastulation but equivalent rates of euploidy, implantation, and live birth compared with blastocysts derived from fresh oocytes, supporting the safety and efficacy of oocyte cryopreservation.