Oral Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

Untangling cryopreservation from biopsy: Effects of repeated cryopreservation alone on embryo viability and post-transfer outcomes (#176)

Tong Li 1 2 , Shan Li 1 2 , Darren Chow 1 2 , Ryan Rose 1 3 , Cheow Yuen (Tiffany) Tan 1 2 , Kylie Dunning 1 2
  1. Robinson Research Institute, School of Biomedicine, The University of Adelaide, Adelaide, SA, Australia
  2. Institute for Photonics and Advanced Sensing, The University of Adelaide, Adelaide, SA, Australia
  3. Monash IVF Group, Clayton, Victoria, Australia

In the IVF clinic, preimplantation genetic testing of embryos is common practice. This involves taking a biopsy for genetic evaluation and subsequent cryopreservation of the embryo. In cases where genetic testing fails to achieve a reliable result, a further round of biopsy and cryopreservation is required. While repeated biopsy and freeze-thaw cycles is known to negatively impact live birth rates, the exclusive impact of multiple rounds of cryopreservation has not been investigated. Here, we evaluate the effect of repeated cryopreservation alone on embryo viability and pregnancy outcomes.

Blastocyst-stage murine embryos were subjected to one, two, or three freeze-thaw cycles with non-cryopreserved (fresh) embryos serving as a control. Outcomes assessed included survival rate of embryos post-thawing and the allocation of cells to the inner cell mass and trophectoderm lineages. We also assessed implantation potential and offspring health following transfer to recipients.

We found that embryos subjected to three freeze-thaw cycles had significantly lower survival rates compared to those that underwent one freeze-thaw cycle (P<0.001). Additionally, the number of cells within the inner cell mass was significantly reduced in embryos subjected to two or three freeze-thaw cycles compared to fresh (P<0.001). Compared to control, embryos subjected to two or three rounds of freeze-thaw cycles had significantly lower pregnancy (~30% reduction, P<0.05) and implantation rates (~54% reduction, P<0.05). Repeated cryopreservation also negatively impacted the fetus and placenta. Specifically, two or three rounds of repeated cryopreservation resulted in reduced fetal weight (P<0.05) as well as a lower fetal to placental weight ratio (P<0.05), when compared to control.

This study is the first to demonstrate the impact of multiple freeze-thaw cycles on embryo implantation potential, pregnancy rate, and offspring health. Our findings hold clinical pertinence and has the potential to inform future guidelines and practices concerning embryo cryopreservation, ultimately contributing to the optimisation of ART.