Science and technology enable us to prevent difficult and unwanted situations. In IVF that fact has a major role. In the field of fertility, the mother-to-be may have a successful conception, pregnancy and delivery, and both parents may have a healthy child free of diseases and birth defects.

Preimplantation genetic testing is the most advanced fertility care to identify in many cases the healthiest embryos, leading to a successful pregnancy.

How does preimplantation genetic testing work?

Before we dive deeper at the types of preimplantation genetic testing, each performed for a different reason, let’s look at how the specific procedure is done.

During IVF the eggs are fertilized by the sperm. From this union arises the zygote which develops into an embryo consisting of an inner cell mass and an outer layer of cells, the trophectoderm which will eventually become the placenta.

To predict the future genetic status of the embryo, as well as the pregnancy, a small number of cells/biopsies are taken from the trophectoderm, without endangering the inner cell mass. Every woman and every situation is different, so the fertility specialist will help you choose the test that meets your own needs. There are three types of preimplantation genetic testing.

Preimplantation Genetic Testing for Aneuploidy (PGT-A)

PGS, also known as preimplantation genetic testing for aneuploidy (PGT-A) is the most common form of fetal screening for aneuploidy and shows whether the fetus has a normal number of chromosomes or not. Almost, every cell in the human body must have 46 chromosomes, when there are too many or too few, genetic disorders such as Down syndrome can occur.

Also, the risk of miscarrying or having a child with a genetic disorder can be reduced by screening embryos with the highest chance of success.

Recent research has shown that PGT-A can sometimes portray positive results that are not true, so further research is being done to make it more effective in the future.

Preimplantation Genetic Testing for Monogenetic Disorders (PGT-M)

With this specific test, it can be detected if there is a specific hereditary condition in the fetus. When one or both partners have a history of genetic conditions in their families, PGT is indicated to screen for:

• Autosomal recessive disorders such as cystic fibrosis, Tay-Sachs disease, thalassemia, spinal muscular dystrophy.
• Autosomal dominant such as myotonic dystrophy, Huntington’s disease, Charlot – Marie-Tooth disease.
• Natural links such as hemophilia A and B, fragile X syndrome, Duchenne muscular dystrophy.

Preimplantation Genetic Testing for Structural Chromosomal Rearrangement (PGT-SR).

A very specific type of certain chromosomal abnormalities can be detected with this genetic test. It is not about a common test that is why it is carried out by very few patients who may have a history of consecutive pregnancy loss, various other problems or have been diagnosed with a chromosomal translocation.

Does PGS testing improve IVF success?

The answer is yes, since it can reduce the chances of miscarriage, since chromosomal abnormality is considered one of the most common causes. Another reason that may contribute to a successful IVF is that embryos with a normal number of chromosomes have a higher chance of implantation leading to pregnancy.

When IVF needs PGT?

If you know you have chromosomal abnormalities or are concerned that you may be carrying a baby with birth defects, it is not only recommended, but required. Otherwise, PGT does not need to be done to start an IVF cycle.

Does PGT harm embryos?

The PGT test has its own risk. As for harming the actual embryo, yes, that is a possibility, and some data shows that embryos can be lost during that procedure.

Does PGT-A harm fetuses?

Since it involves taking a biopsy, after removing a number of cells or a cell from the embryo, there is the possibility of damage that can affect its development once it is transferred to the uterus.

Are there any reasons not to do PGT?

The truth is that there are two main concerns, the first one, as it has been already reported, is the possibility to cause harm to the fetus. The second concerns the possibility of preventing the implantation of an embryo that may have a normal number of chromosomes but the test results may show the opposite.

It is very important for prospective parents to be aware of their family history of birth defects and to decide in full cooperation with their doctor when undergoing IVF, whether and what type of preimplantation genetic testing is appropriate for a safe and successful pregnancy.