Comparison of in-vitro outcomes from cryopreserved oocytes and sibling fresh oocytes

Abstract

In Italy, the restrictive IVF law generalizes the indication for oocyte freezing for surplus oocytes in 78.5% of in-vitro assisted reproductive cycles. With a view to understanding better what the prospects for intracytoplasmic sperm injection (ICSI) on frozen-thawed oocytes might be, the consequences of freeze-thaw procedures on fertilization, cleavage rates and embryo quality obtained from frozen-thawed oocytes were studied and compared with the results obtained from sibling fresh oocytes. Eleven IVF and 29 ICSI on 76 and 169 fresh oocytes were performed and the corresponding 40 ICSI on 221 sibling frozen-thawed oocytes. There was no difference in terms of fertilization rate between fresh and sibling frozen-thawed oocytes. The cleavage rate (98.0 and 94.4% with fresh oocytes in IVF and ICSI; 77.3% with frozen-thawed oocytes in ICSI; P < 0.001) and embryo quality (grade I embryos over total embryos: 36.7 and 22.2% with fresh oocytes in IVF and ICSI; 12.1% with frozen-thawed oocytes in ICSI; respectively P < 0.001 and P < 0.05) were statistically lower after oocyte cryopreservation. The significant decrease in meiotic spindle retrieval rate before freezing (62.4%) and after thawing procedures (43.4%; P < 0.001) suggests that cryoconservation induces irreversible damage to microtubule repolymerization. The consequences of oocyte cryopreservation procedures on embryo development are reviewed.

Implantation rates of embryos generated from slow cooled human oocytes from young women are comparable to those of fresh and frozen embryos from the same age group

“…The survival rate achieved in the present study is similar to that previously observed with the 0.3 M sucrose method [7,15,16,[31][32][33][34][35][36][37] and the 0.2 M sucrose method [17,19,21]. In some of the above studies only oocytes with optimal morphology were cryopreserved [37,38] which is not the case in the present study.…”

Impact of oocyte cryopreservation on embryo development

“…The results reported here are in agreement with previous data generated on a small number of cases (43,44) reporting on a slower cleavage rate in frozen cycles when compared with the sibling fresh oocytes. This behavior suggests that even if surviving thawing, the process of oocyte cryopreservation by slow freezing has a negative effect on the potential of further growth that is evident as early as the first cleavage divisions.…”

The accumulation of vitrified oocytes is a strategy to increase the number of euploid available blastocysts for transfer after preimplantation genetic testing

“…Oocyte denudation was performed 2 h after oocyte retrieval. ICSI was performed 1 h after oocyte denudation on fresh oocytes and 1 h after warming and in vitro culture on vitrified oocytes with the same sample of partner’s freshly ejaculated spermatozoa sample as previously described [22]. …”