Optimizing human oocyte cryopreservation for fertility preservation patients Should we mature then freeze or freeze then mature

Germinal vesicle and metaphase I oocytes should be matured in vitro before cryopreservation to optimize the reproductive potential of all retrieved oocytes.

Joseph A. Lee, B.S., Jason Barritt, PhD., Rose Marie Moschini, B.S., Richard E. Slifkin, B.S., Alan B. Copperman, M.D.

Volume 99, Issue 5, Pages 1356-1362, April 2013


To evaluate a timely implementation of In Vitro Maturation (IVM) of any immature oocytes with an optimal freezing protocol is essential. We evaluated the maturation and post-thaw survival rates of immature oocytes to determine whether or not IVM should be attempted prior to or after cryopreservation.

Nonrandomized observational study.

Private academic and clinical reproductive center.

Patients (n=71) who donated immature unusable oocytes following vaginal oocyte retrieval (VOR) after undergoing controlled ovarian hyperstimulation using a standard gonadotropin-releasing hormone GnRH antagonist protocol.

Germinal Vesicle (GV), Metaphase I (MI) and Metaphase II (MII) oocytes (n=175) were obtained from consenting IVF patients for either a Fresh IVM, Post-Thaw IVM or control group. In the Fresh IVM group, GV and MI-stage oocytes (n = 69) were cultured for 24-hours, matured In Vitro (IVM-MII), cryopreserved, thawed and evaluated for survival. In the Post-Thaw IVM group, GV and MI-stage oocytes (n=27) were frozen on Day 0, thawed, evaluated for survival and cultured for 24-hour IVM. MII donor oocytes (n=79) were cryopreserved and thawed as a control.

Main Outcome Measures:
Survival post-freeze and oocyte development to MII-stage was analyzed using Chi-Square analysis.

Fresh IVM had a significantly higher maturation rate than Post-Thaw IVM (p<0.05). Conclusions:
Oocyte cryopreservation is important for patients at risk of ovarian cancer, elective fertility preservation and potentially for ovum donation. The superior maturation rate of GV and MI oocytes in the Fresh vs. Post-thaw groups provides strong evidence for maturing oocytes to the MII stage prior to cryopreservation.

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