Related Experiment Video
Updated: May 10, 2026
Modified MicroSecure Vitrification: A Safe, Simple and Highly Effective Cryopreservation Procedure for Human Blastocysts
Published on: March 2, 2017
Developing a decision support tool to optimize oocyte thawing for producing at least three euploid blastocysts
Emily A Clarke1, Carlos Hernandez-Nieto2, Michelle Bayefsky1
1Department of Obstetrics, Gynecology, and Reproductive Science, Icahn School of Medicine at Mount Sinai, New York, NY; Reproductive Medicine Associates of New York, New York, NY.
Objective:
To assess the optimal number of oocytes needed to thaw to yield ≥3 euploid blastocysts.
Design:
Retrospective cohort study.
Subjects:
Patients who underwent oocyte cryopreservation and returned for thaw between 2012 and 2024 at a single academic-affiliated fertility clinic. Patients were grouped by number of oocytes thawed (group A: 2-8, group B: 9-11, group C: 12-16, and group D: >16 oocytes). Patients were excluded if they did not use preimplantation genetic testing for aneuploidy, had multiple cryopreservation cycles combined within one thaw cycle, or opted for fresh embryo transfer.
Exposure:
Number of oocytes thawed.
Main Outcome Measures:
Primary outcome was the number of oocytes needed to thaw to produce ≥3 euploid blastocysts. Secondary outcomes included oocyte thaw laboratory outcomes. Subgroup analysis was performed by age groups at cryopreservation (<35, 35 to <38, 38 to <41, and ≥41 years).
Results:
A total of 417 oocyte thaw cycles were included. Overall, 50.0% of patients in group D (>16 oocytes thawed, n = 104 cycles) achieved ≥3 euploid blastocysts, compared with 27.7% in group C (12-16 oocytes, n = 101), 16.5% in group B (9-11 oocytes, n = 103), and 5.5% in group A (2-8 oocytes, n = 109). In age groups <35 and 35 to <38, compared with thaw group D, patients in thaw group C had similar odds of producing ≥3 euploids (<35: adjusted odds ratio [aOR] 0.47 [0.17-1.34]; 35 to <38: aOR 0.45 [0.19-1.10]); however, thaw groups A and B had significantly lower chances compared with group D (<35 years: group A: aOR 0.13 [0.04-0.50], group B: aOR 0.10 [0.03-0.41]; and 35 to <38 years: group A: aOR 0.06 [0.01-0.28], group B: aOR 0.45 (0.34 [0.13-0.88]). Patients in age groups ≥38 years (n = 118) produced ≥3 euploid blastocysts in only 3.4% of cycles.
Conclusion:
In patients <38 years, thawing 12-16 oocytes yields similar chances of producing ≥3 euploid blastocysts compared with thawing >16 oocytes. Patients with <12 vitrified oocytes should thaw all available oocytes or, if limited, should consider additional cryopreservation cycles. Conversely, patients with many vitrified oocytes may consider limiting the thaw to 16 oocytes, because thawing all does not appear to provide additional benefit in achieving one live birth.
