Comparison of embryo quality between sibling embryos originating from frozen or fresh oocytes

Abstract

Human embryo cryopreservation techniques allow storage of surplus embryos created during assisted reproduction procedures; however, the existence of these same surplus embryos has sparked further debate. What can be their fate once they are no longer desired by their parents, or if the parents are deceased? Thus, the level of interest in the cryopreservation of oocytes has increased, as has the necessity for further scientific study. This study had the objective of comparing embryo quality from 16 women who underwent intracytoplasmic sperm injection, where approximately half of the retrieved oocytes per cycle were inseminated fresh after collection, and the remainder cryopreserved for subsequent fertilization. Normal fertilization rates were not significantly different between the two oocyte-treatment groups. There was no significant difference in the frequency of good quality embryos (morphology grades I and II) on the second day of laboratory evaluation between embryos derived from the two oocyte-treatment groups. It is interesting to note that embryo transfer from fresh oocytes produced no pregnancies, which shows that even embryos derived from frozen oocytes that are fragmented or have a slower cleavage rate are viable embryos, capable of producing healthy babies.

Human oocyte cryopreservation

“…In mouse oocytes, the presence of sodium in the solute during cryopreservation was shown to be detrimental when compared with replacement with choline (Stachecki et al, 1998). However, clinical results for human oocyte cryopreservation in sodium-depleted media show no further improvement over the increase already observed with higher sucrose with 52% of oocytes surviving cryopreservation in sodium-depleted medium containing 0.1 M sucrose (Quintans et al, 2002;Stachecki et al, 2006), 62% in similar medium with 0.2 M sucrose (Quintans et al, 2002;Boldt et al, 2003;Azambuja et al, 2005;Petracco et al, 2006;Stachecki et al, 2006) and 59% with 0.3 M sucrose (Boldt et al, 2006).…”

“…However, no equivalent comparative data are available on human oocytes. Cryopreservation in sodium-depleted medium containing PROH and 0.1 M sucrose resulted in two births (Quintans et al, 2002), a further nine births have been reported in similar medium containing 0.2 M sucrose (Azambuja et al, 2005;Boldt et al, 2006;Petracco et al, 2006), and five births have been reported from the application of this approach in the presence of 0.3 M sucrose (Boldt et al, 2006). These clinical studies are on small series of patients (,25).…”

Slow controlled-rate freezing of human in vitro matured oocytes: effects on maturation rate and kinetics and parthenogenetic activation

“…Other reports have not detected any differences in fertilization rates (23,26,32). To check if human oocytes can maintain their ability to activate after our slow controlled-rate freezing protocol, we artificially activated frozen/thawed oocytes and compared the outcome with that of fresh oocytes as a control.…”

Oocyte cryopreservation: a technical and clinical update

“…Replacing sodium with choline is considered another enhancement that can be applied to slow-freezing protocols. It was first implemented in mice [56,108] but was later shown to improve human oocyte post-thaw survival and pregnancy rates [22,109,110].…”