Aneuploidy and PGT/A

Aneuploidy is a major source of adverse outcomes in human reproduction, the impact is so severe that American College Of Obstetricians and Gynecologyists now recommend universal screening. They have concluded that there is no age group or clinical setting where the risk of aneuploid gestationis low enough that screening is not beneficial (see reference 1).

More than 70% of spontaneous miscarriages are due to chromosomal aneuploidies. PGT/A helps to shorten the time to a viable pregnancy by reducing the need of multiple IVF cycles. Euploid embryo transfer results in highest pregnancy rates and live birth rates reducing miscarriage risk independent of maternal age (see reference 2).

It has been recently completed a detailed analysis of more than 11.000 PGT/A cycles with cryo-preserved embryo transfer cycles and assessed the total costs of infertility care defined as total costs to either attain a delivery or exhaust the available cohort of embryos and compared them to costs of cycles without PGT/A. The date clearly demonstrated that the total cost of infertility care is lower when using PGT/A when two or more blastocysts are available to be screened (see reference 3).

Selection of chromosomally normal embryos for transfer by aneuploidy screening has been a primary focus of investigation since the inception of PGS. Array comparative genomic hybridization has been proven to be a reliable method for preimplantation genetic screening within 24 hours and has been widely applied in IVF-PGS treatment cycles worldwide.

In a study conducted by Yang Z a total of 164 WGA products derived from 38 IVF-PGS treatment cycles were analyzed with aCGH in comparison to NGS. The testing results from the same WGA products were compared between the two methods. The highly validated method for aneuploidy screening, aCGH provided a 100% 24-chromosome diagnosis (of euploid and aneuploid) consistency with NGS. In this study, it has been provided further clinical evidence demonstrating that aCGH screening has resulted in similarly high ongoing pregnancy and implantation rates compared to NGS screening (see reference 4).

This is confirmed by another study in which it has been demonstrated the efficacy in utilizing blastocyst biopsy with PGT/A by array CGH ; the results generated affirm the safety of blastocyst biopsy through reduced SAB (spontaneous abortion) results and the lack of abnormalities being reported among newborns.

These findings confirm the belief that blastocysts are the ideal stage for biopsy intervention and that PGT/A, in conjunction with vitrified warmed embryo transfers, is an ideal option to efficiently succeed in transferring a single embryo. The results not only showed an increase in pregnancies in all age groups, but it also effectively reduced miscarriage rates. Additionally it was demonstrated an increase in implantation rate and live birth rate in each considered age group treated with PGT/A which reinforces the benefits gained by the routine IVF commitment to the clinical application of PGT/A per transfer (see reference 5).

References

1 Rosenwaks Z at al , The pros and cons of preimplantation genetic testing for aneuploidy : clinical and laboratory perspectives, Fertil Steril Aug 2018

2 Parikh F et al , Preimplantation Genetic Testing: Its Evolution, Where Are We Today? J Hum Reprod Sci. 2018

3 Neal S et al. , Single embryo transfer (SET) following comphrehensive chromosome screening (CCS) is more cost effective than unscreened sequential SET. Fertil Steril 2016

4 Yang Z et al , Randomized comparison of next-generation sequencing and array comparative genomic hybridization for preimplantation genetic screening: a pilot study ; BMC Medical Genomics 2015

5 Whitney J et al , Single center validation of routine blastocyst biopsy implementation ; J Assist Reprod Genet (2016)