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Cristina Gonzalez lecture at the Spanish Fertility Society

SEF2018

The use of devitrified oocytes does not decrease the number of transferable embryos after PGS.

Introduction

The use of donor bank vitrified oocytes is becoming more and more frequent due to the advantages offered by gamete banks with respect to treatment planning for recipients and the security of having a certain number of mature oocytes available, avoiding in advance the possible cancellation of a treatment due to the non-recovery of mature oocytes in an ovarian puncture. Some authors have reported that the vitrification and devitrification processes can affect various oocyte components such as the mitotic spindle in a way that could decrease the rate of euploid embryos derived from devitrified oocytes.


Objective

The objective of this study is to analyze whether vitrification-desvitrification processes of oocytes can influence the generation of a lower number of euploid embryos and transferable mosaics.


Material and methods

56 PGS treatments between the years 2017 to early 2019 were retrospectively analyzed. 28 treatments were performed from fresh donor oocytes or from patients under 35 years of age and 28 were from donor oocytes or patients under 35 years of age, but which were previously vitrified. The resulting embryos were cultured to blastocyst stage in single medium in a 7%CO2 / 5%O2 atmosphere  being observed only on the day of fertilization and on day +5/+6 for trophectoderm biopsy and subsequent vitrification. We analyzed 118 blastocysts from fresh oocytes and  97 from devitrified oocytes. All of them underwent PSG by NGS.


Results

The mean age of the donors and/or patients was 25.7 for the fresh oocyte group and 24.2 for the devitrified oocyte group. The mean number of MII microinjected was 8.6 for the fresh oocyte treatment group and 7.8 for devitrified oocytes. Of the 118 blastocysts biopsied from fresh oocytes, 55 were euploid and 14 were mosaic transferable for a total of 69 transferable blastocysts. Of the 97 blastocysts analyzed derived from devitrified oocytes, 55 were euploid and 6 were mosaic transferable (Table I). The percentages of transferable embryos were 58.5% and 62.9%, respectively (Table I). By Student’s t-test we can assume that there are no statistically significant differences in the means (0.459>0.05) of euploid blastocysts generated from fresh or devitrified oocytes with a 95% confidence interval.

Conclusions

According to our results and under our working conditions we can advise the use of vitrified oocytes for PGS treatments since there is no evidence that fewer euploid embryos are produced from these oocytes and they offer the same potential as fresh oocytes being good candidates for PGS programs. However, our N is limited because PGS with donor oocytes is not yet a widespread practice although we now know that these oocytes are not free of considerable rates of aneuploidy.