Genetic Testing

Preimplantation Genetic Testing (PGT)

PGT is a procedure that is performed in conjunction with IVF. It is designed to help detect genetic abnormalities/inherited genetic diseases in embryos before implantation, thereby minimizing the transfer of affected embryos.

Preimplantation Genetic Testing - Aneuploidy (PGT-A)

Normal human cells contain 46 chromosomes located in the nucleus of the cell. Chromosomes carry the genetic information in the form of DNA. Every human being receives 23 chromosomes from each parent. If an error occurs leading to the egg or sperm having a missing or extra chromosome, the embryo created will also have a missing or extra chromosome. This condition is called aneuploidy. Most of the aneuploidies will not result in implantation of the embryo, but certain aneuploidies, such as trisomy 21, can implant and lead to Down’s syndrome. Some other common aneuploidies include trisomy 13, trisomy 18, and Klinefelter's syndrome (XXY).

Who Should Consider Preimplantation Genetic Testing?

PGT is indicated for patients who have a history of recurrent miscarriages, advanced maternal age (≥38 years), repeated IVF failures in spite of high-grade embryos, unexplained infertility, severe male factor infertility, or inherited genetic disorders (e.g., cystic fibrosis, Tay Sachs disease, Myotonic dystrophy, etc.). Currently, there are more than 1000 types of single gene mutations that can be diagnosed.

Procedure

In order to perform genetic testing on an embryo, several cells from the trophectoderm layer are extracted on fifth, sixth or seventh day of development. This procedure is called an embryo biopsy. The extracted cells are sent out for analysis to Cooper Genomics and/or Ingenomix. Subsequently, the biopsied embryo is vitrified. After the results are received, patients will have the normal embryo transferred back.

What Are the Benefits of PGT?

Patients who are carriers of single gene mutations can avoid transmitting those disorders to their offspring by testing the embryos and choosing not to transfer those which are affected or carriers.

Patients who have had several miscarriages in the past can benefit from PGT-A for aneuploidy screening by avoiding the transfer of embryos that are aneuploid and will eventually fail to implant. The likelihood of having a trisomic pregnancy increases with advanced maternal age (>38 years). 

PGT-A allows selection of normal embryos at the pre-implantation stage and reduces the chance of detecting abnormal fetal development during an aminocentesis in the second trimester. Patients who failed several IVF attempts and are known to generate good cohorts of embryos might have a high rate of aneuploidy and can benefit by PGT-A. 

Another group of patients who can benefit from PGT are those who carry translocations, which are detected by karyotyping.

Does PGT Come with Any Risks?

There are certain risks associated with any micromanipulation procedure, but these are minimal. Trophectoderm biopsy does require embryos to develop to the blastocyst stage before the biopsy is performed. Not all couples will have embryos that develop to this stage. Occasionally, results are not able to be determined.