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Preimplantation Genetic Testing (PGT)

Embryo testing prior to transfer can improve implantation rates and increase the chances of having a healthy baby. Learn about the types of Preimplantation Genetic Testing, its benefits, how PGT actually works, if it's safe, and more.

What is Preimplantation Genetic Testing?

PGT (Preimplantation Genetic Testing) is an umbrella term for three types of embryo screening, PGT-A, PGT-M, and PGT-SR. With these three types of tests, a person can learn much about their embryos created through in vitro fertilization or IVF. Overall, PGT is an accurate and safe test that can increase a family’s chance of having a successful pregnancy.

Who Should Use PGT?

It’s important to talk to your doctor or genetic counselor to determine if PGT is right for you.


The older you are, the greater the chance of finding a chromosome problem in embryos. Those over 42, for instance, have an 80 to 85% chance of finding an issue. Those under 30 have a 20 to 25% chance for each embryo to be chromosomally abnormal.

There are three types of PGT and each is indicated for a different reason. PGT-A can be used in any IVF cycle to determine the number of chromosomes, therein the embryo viability, PGT-M is more useful for those with a family history of specific, single-gene diseases and PGT-SR is best for cycles where a parent has a particular chromosome rearrangement.

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The 3 Types of PGT

Preimplantation genetic testing for aneuploidy (PGT-A):

Formerly known as PGS, PGT-A looks for extra or missing chromosomes. It’s offered to anyone going through IVF. PGT-A is unable to detect single-gene disorders or birth defects like congenital heart disease, cleft lip and palate, and spina bifida.

The “-A” in PGT-A stands for aneuploidy, or an abnormal amount of chromosomes within the embryo. The term euploid is given to embryos that have the correct number of chromosomes.

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Preimplantation genetic testing for monogenic disorders (PGT-M):

Formerly known as PGD, PGT-M screens for inherited conditions and diseases caused by a mutation in a single gene (i.e. cystic fibrosis). It’s only offered to those with an increased chance of passing on a specific inherited condition.

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Preimplantation genetic testing for chromosome structural rearrangements (PGT-SR)

This test is designed for those with a chromosome rearrangement, such as a translocation or inversion, which puts them at increased risk of creating embryos with unbalanced chromosome issues.

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How Does PGT Work?

During IVF, doctors can carefully remove a few cells from the embryo’s outer ridge of cells that later develop into the placenta. This is usually conducted on Day 5 or 6 of development when they have reached what’s called the “blastocyst stage.” After the biopsy is safely performed, the embryos are then frozen while the sampled cells are analyzed for chromosome or genetic issues.

The Benefits of PGT

While there are many benefits to choosing Preimplantation Genetic Testing, let's break down four of the main benefits and why they're important here. Each of these has a clear upside, but depending on your health history or genetic concerns, certain benefits may stand out to you personally.

Increased implantation rate

Because PGT uncovers issues with genetic traits or chromosomal makeup, you can better select a healthier embryo, resulting in improved pregnancy rates.

Increased chance of having a healthy baby

PGT is able to identify potential birth defects, inherited conditions and diseases, and chromosomal arrangement. Knowing this prior to an embryo transfer will help in the selection of a healthier embryo.

Decreased risk of a miscarriage

Sometimes a miscarriage can occur because of a chromosome issue or another genetic anomaly. Knowing of any issues prior to transfer helps in the selection of the best possible embryo.

Reduction in multiple births

PGT-A can be combined with elective single embryo transfer (e-SET) so one single embryo is transferred instead of two or more. Knowing that the embryo has been deemed chromosomally fit makes it easier to decide to transfer only one embryo.

How Accurate is PGT?

PGT is an incredibly safe and effective process, with accuracy rates of 98 to 99%.

However, it is not a perfect system and has a misdiagnosis rate of 1 to 2%. False negatives (where embryos are said to be normal but have an abnormality) or false positives (where the opposite is true) are examples of misdiagnosis. Due to the limitations of the test, PGT laboratories state that the testing should not be considered a replacement for prenatal diagnosis. Overall, PGT is very accurate at discovering abnormal numbers of chromosomes and specific genetic issues or mutations.

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Associated Risks with PGT

Overall, PGT is considered safe with no known increase in associated risk of birth defects or genetic disorders.

The biopsied cells are removed from the outer ridge of the embryo that ultimately becomes the placenta, not the fetus, which limits the risks.

Also, these same cells can be used for PGT-A, PGT-M, and PTG-SR. That said, there is always a slight chance that removing the cells from the trophectoderm could damage or disrupt the embryo. The risk of this is said to be less than 1%.

At Illume Fertility, your doctor, genetic counselor, and medical support team will discuss all options with you and help you choose the ones that are most likely to result in a healthy baby.

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Explore More Family Building Resources

Beginning fertility treatment can be overwhelming at times, but educating yourself about the process can help you feel more in control and assure you that you are making the best possible decisions for you and your family.

Take a look around for more information, from how to be your healthiest prior to conception to holistic options that can improve success rates and increase overall wellbeing.

We are here to help you navigate your own unique fertility journey.

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