April 5, 2021

Genesis Genoma Lab: Preimplantation Genetic Testing for Aneuploidies (PGT-A)

Chromosomal aneuploidies are considered the main cause of failed embryo development, implantation failure and early pregnancy loss. Preimplantation Genetic Testing for Aneuploidies (PGT-A) is an embryo screening technique used to identify chromosomally normal (euploid) embryos conceived by assisted reproduction technology, in order to select those that have a better chance of leading to a successful pregnancy. By identifying euploid embryos, PGT-A aims to eliminate the advanced maternal age effect and increase implantation and live birth rates, reduce miscarriage rates and abnormal pregnancies, as well as reduce time to pregnancy.

Currently, PGT-A is offered to women of advanced reproductive age (>38 years) who undergo IVF, couples with recurrent miscarriages and normal parental karyotypes, recurrent implantation failure, as well as  severe male factor infertility.

Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR) can be offered to carriers of balanced translocations, in order to avoid the possibility of producing chromosomally imbalanced offspring.

The advancements of techniques such as blastocyst stage biopsy, embryo cryopreservation through vitrification, along with the development of novel molecular methodologies allowing the comprehensive screening of all 24 chromosomes, such as array comparative genomic hybridization (aCGH) have provided infertile couples a new option for achieving pregnancy.

Genesis Genoma Lab utilizes an oligonucleotide microarray platform that provides the ability to detect aneuploidies, as well as segmental aneuploidies larger than 10 Mb. After analysis embryos are classified as either “euploid” and their transfer is recommended or as “aneuploid” and their transfer is discouraged. In rare cases (e.g. mosaicism) genetic counselling may be offered regarding an embryo that was tested and findings were inconclusive.

The results are available in less than 24 hours from sample receipt for fresh IVF cycles and 7-10 days if the embryos will be frozen.

Overview of the procedure

Couples meet with a genetic counsellor who receives their medical history, informs them on the advantages and limitations of the PGT-A procedure and answers all possible questions.

Couples start an IVF cycle that includes oocyte and sperm retrieval and in vitro fertilization. The resulting embryos are then biopsied at the 5th day of development, and a few cells are removed.

Embryo biopsies are transferred to the genetics laboratory where amplification of the cell genome is performed (WGA) in order to be analyzed for chromosomal aneuploidies with the aCGH platform.

After testing is completed the final report is sent to the IVF clinic, in order for the euploid embryos to be transferred.