Pre‐implantation genetic testing for aneuploidy: the past, present and future

Live birth rate following a euploid blastocyst transfer is not affected by double vitrification and warming at cleavage or blastocyst stage

PURPOSE

To compare reproductive outcomes following a euploid embryo transfer, between those embryos vitrified-warmed twice to those vitrified-warmed once.

METHODS

We retrospectively analysed 694 single euploid frozen embryo transfer cycles following preimplantation genetic testing for aneuploidy (PGT-A). For cycles in group 1 (N = 451), embryos were biopsied for PGT-A at blastocyst stage and vitrified. For cycles in group 2 (N = 146), embryos were vitrified at blastocyst stage, before being warmed and biopsied for PGT-A and vitrified again. For cycles in group 3 (N = 97), embryos were vitrified on day-3, before being warmed, cultured to day-5 and biopsied for PGT-A and re-vitrified.

RESULTS

The pregnancy, clinical pregnancy and livebirth rate in group 2 were not statistically different to group 1 (pregnancy rate, adjusted OR 1.09, 95% CI 0.62-1.91; clinical pregnancy, aOR 0.89, 95% CI 0.58-1.37; live birth rate, aOR 0.85, 95% CI 0.56-1.28). There was also no significant difference between group 3 and group 1, with similar pregnancy rate (aOR 1.22, 95% CI 0.74-1.99), clinical pregnancy rate (aOR 1.21, 95% CI 0.75-1.96) and live birth rate (aOR 1.15, 95% CI, 0.73-1.80). There was no significant difference in miscarriage rates between all three groups. The age at the oocyte collection, embryo quality and day of biopsy were associated with pregnancy, clinical pregnancy and live birth rate.

CONCLUSION

This study suggests that vitrifying and warming embryos twice at blastocyst or at cleavage and then blastocyst stage, can lead to similar reproductive outcomes to embryos vitrified-warmed once, after a single euploid embryo transfer.

Preimplantation Genetic Testing for Aneuploidy: Current Perspectives

Despite improvements in assisted reproduction techniques (ARTs), live birth rates remain suboptimal, particularly in women with advanced maternal age (AMA). The leading cause of poor reproductive outcomes demonstrated in women with AMA, as well as women with recurrent miscarriage and repetitive implantation failure, is thought to be due to high rates of embryonic aneuploidy. Preimplantation genetic testing for aneuploidies (PGT-A) aims to select an euploid embryo for transfer and therefore improve ART outcomes. Early PGT-A studies using fluorescent in situ hybridization on mainly cleavage-stage biopsies failed to show improved delivery rates and, in certain cases, were even found to be harmful. However, the development of comprehensive chromosome screening, as well as improvements in culture media and vitrification techniques, has resulted in an emerging body of evidence in favor of PGT-A, demonstrating higher implantation, pregnancy, and live birth rates. While there are concerns regarding the potential harm of invasive biopsy and the cost implications of PGT-A, the introduction of noninvasive techniques and the development of new high-throughput methods which lower costs are tackling these issues. This review aims to assess the evidence for PGT-A, address possible concerns regarding PGT-A, and also explore the future direction of this technology.