Genetic Testing

Genetic Testing – Preimplantation Genetic Testing (PGT)

Preimplantation Genetic Testing is a process is to evaluate the chromosomal makeup of an embryo and to look for other specific genetic abnormalities. This technology, known as next-generation sequencing, enables the evaluation of embryos for problems prior to transferring them into the uterus, thus increasing the probability of a having a normal pregnancy. PGT can be categorized into three groups. PGT-A (for aneuploidy), PGT-M (for monogenic disorders) and PGT-SR (for chromosomal structural rearrangements)

PGT-A

Because the majority of miscarriages are due to chromosomal abnormalities, many couples undergo PGT in order to select embryos that are chromosomally “normal” and increase their chances of success with IVF. An embryo with too many or too few chromosomes (aneuploidy) may result in the following:

1. Failure of implantation in the uterus

2. Pregnancy loss (miscarriage)

3. Abnormal pregnancy such as Down Syndrome (trisomy 21) or Edward’s Syndrome (trisomy 18)

PGT-A can also be used for gender selection (boy or girl) in situations where couples desire family balancing or who are at risk for having a child with a sex-linked disease.

PGT-M

This type of genetic abnormality is useful for evaluation of couples with heritable genetic mutations carried by one or both parents. One common example of a monogenic disorder is Cystic Fibrosis (CF), a disorder of the lungs that can result from parents who are both genetic carriers of the genetic mutation that is responsible for the disease. People who are carriers of this disorder are not affected with CF due to the fact they have one normal, matching gene in their double stranded DNA. If, however, an embryo is produced that inherits both abnormal genes (one from the mother and one from the father), Cystic Fibrosis will result. Thus, when both parents are carriers, the risk of conceiving a baby with CF is 25%.

PGT-SR

This genetic problem results when there is a structural rearrangement of a segment of a chromosome that can result in an abnormal embryo, destined to miscarry. This problem occurs when one of the parents whose chromosomes are “balanced” such that the parent is healthy and unaware of this genetic problem. In this situation, when gametes (sperm or eggs) are produced by the affected parent, the gamete are very often “unbalanced”, resulting in an abnormal embryo, either lacking or having too much genetic material.

Should I have genetic testing/PGT performed on my embryos?

This depends on a number of factors including your age, medical history, and other risk factors. As a rule, genetic testing can improve pregnancy rates by identifying those embryos that are most likely to make a baby.