Preimplantation Genetic Testing: PGT and Advanced PGT

Preimplantation genetic testing is the assessment of embryos created during IVF treatment for specific genetic or chromosomal characteristics before embryo transfer. It is widely known as PGT (preimplantation genetic testing) and was formerly called PGD (preimplantation genetic diagnosis). Also referred to as embryo genetic testing or genetic testing in IVF, the specific test used is chosen according to the couple's medical history and the genetic condition being investigated.

With the advanced genetic assessments offered at our clinic, the likely maternal or paternal origin of a chromosomal abnormality can be investigated where appropriate, and a genetic match check can be performed between the embryo and samples taken from the parents. Alongside standard chromosome screening, this information can support treatment planning and quality control.

What Is PGT and Why Is It Performed?

PGT is based on laboratory analysis of a cell sample taken from the embryo. Depending on the case, the aim may be to assess chromosome number, to look for a known structural chromosomal rearrangement, or to check whether a specific genetic disease present in the family has been passed on to the embryo.

Who is PGT recommended for? The answer depends on this purpose. In cases such as a known genetic disease in the family, a structural chromosomal rearrangement in one of the parents, recurrent pregnancy losses or recurrent implantation failure, PGT may be considered as part of IVF treatment.

Not every PGT method provides the same information. That is why, before testing, it should be explained which condition is being investigated, what results can be obtained and what the method's limitations are. Having PGT does not mean the embryo has been screened for all genetic diseases.

PGT-A vs PGT-M vs PGT-SR: What Is the Difference?

The types of PGT differ according to the genetic question being investigated. The test that is right for one couple may not be necessary for another.

The older term PGS (preimplantation genetic screening) largely corresponds to what is now called PGT-A. PGD, on the other hand, covers the tests now known as PGT-M and PGT-SR. This distinction is essentially the difference between PGD and PGS.

When planning PGT-M or PGT-SR, the genetic reports of both parents are reviewed. Depending on the method, additional samples and laboratory preparation may be needed before treatment.

Does Every IVF Patient Need PGT-A?

There is no proven benefit to using PGT-A routinely for every IVF patient. The decision takes into account age, the expected number of embryos, previous treatments, pregnancy losses and the couple's expectations together.

PGT-A does not repair an embryo's chromosomes or create new embryos. It provides information about the existing embryos to help with the transfer decision. That is why the possible benefit, cost and limitations of the test should be discussed individually. The PGT success rate cannot be expressed as a single number either; it varies with factors such as maternal age and the number and quality of embryos.

How Is an Embryo Biopsied for Genetic Testing?

Today, in most PGT cycles the sample is taken once the embryo reaches the blastocyst stage. The biopsy is taken from the outer cell layer (trophectoderm), which later contributes to the placenta. The day of the procedure may vary depending on how the embryo develops.

The cells are sent to the genetics laboratory, and the embryos are usually frozen while the results are awaited. How long PGT results take depends on the method and the laboratory. Biopsy requires an experienced team and suitable laboratory conditions. Possibilities such as an insufficient sample or an inconclusive analysis are also covered in the pre-test consultation.

Advanced PGT: What Is Advanced Genetic Assessment?

On this page, Advanced PGT refers to the additional genetic assessments performed at our clinic. Information on parental origin and genetic matching, which is not always included in a standard PGT-A report, can be investigated with the appropriate analyses.

The scope of the analysis depends on the laboratory method used and the suitability of the samples. Therefore, it should not be assumed that Advanced PGT will give results in the same detail for every embryo.

Can We Tell Whether a Chromosomal Abnormality Comes From the Egg or the Sperm?

With suitable genetic methods, it is possible to investigate whether a chromosomal abnormality in the embryo may have originated from the egg or the sperm. By analysing genetic data from the mother, the father and the embryo together, additional information about the origin of the abnormality can be obtained.

Some methods can also help assess whether the abnormality arose during egg or sperm formation, or during cell divisions after fertilisation. However, parental origin and the origin of the cell division are different questions, and it may not be possible to determine both with certainty in every result.

How Can a Paternal-Origin Finding Influence Treatment?

Detecting a chromosomal abnormality of paternal origin can help to review sperm assessment and personalised sperm selection strategies. The findings are evaluated together with previous fertilisation and embryo development outcomes.

That said, identifying the origin alone does not show which sperm selection method will be more successful, nor does it guarantee that a chromosomally normal embryo will be obtained in the next treatment.

The aim is not to blame either the mother or the father, but to plan treatment with more accurate biological information. A change of parental origin does not necessarily mean that the parent has a hereditary disease.

Can the Embryo's Genetic Match With the Parents Be Verified?

As part of the advanced assessments offered at our clinic, the genetic data obtained from the embryo biopsy can be compared with samples taken from the mother and father to verify the genetic match.

This adds an extra layer of safety and quality control on top of the identity verification and sample tracking procedures used throughout IVF. The genetic match check is designed to confirm which parents the embryo comes from; it is not a test showing that the embryo is free of all diseases.

Euploid, Aneuploid and Mosaic PGT Results: What Do They Mean?

The terms used in PGT reports describe the findings in the tested cell sample. Results should be interpreted in light of the laboratory's method and reporting criteria.

A mosaic result does not mean that every cell of the embryo has been examined individually. The biopsy represents a limited number of cells, and technical factors can also affect the result. The mosaicism percentage in the report should not be read as the proportion of the embryo or the future baby that is affected.

What Happens If No Euploid Embryo Is Found?

If no euploid embryo is found, the available results are reviewed together with the genetics laboratory and the treatment team. A mosaic result, an aneuploid result and an analysis that gave no result are different situations.

Options may include a new egg collection cycle, a detailed review of the reports on the existing embryos, or discussing the transfer of a suitable mosaic embryo. Which path is considered depends on the couple's circumstances.

Not having a euploid embryo does not mean that every embryo reported as aneuploid can be transferred.

Can a Mosaic Embryo Be Transferred?

Some chromosomal differences can arise during mitotic cell divisions after fertilisation and may be linked to a mosaic result. In suitable cases, embryos with a mosaic result may be considered as a transfer option.

This assessment considers the reported level of mosaicism, the type of change, the chromosomes involved, embryo quality, the status of the other embryos and the couple's clinical history together. The decision is never based on a single percentage.

Healthy births have been reported after mosaic embryo transfer. However, some studies have shown lower implantation and higher miscarriage rates compared with euploid embryos. Outcomes are not the same for every mosaic embryo.

At our clinic, if a suitable euploid embryo is available for transfer, it takes priority. Mosaic embryo transfer is only considered after detailed genetic counselling and an individual medical assessment.

Is Genetic Testing During Pregnancy Still Needed After PGT?

Having PGT does not remove the need to consider screening and diagnostic options during pregnancy. The scope and limitations of the test are also taken into account in pregnancy follow-up.

Genetic counselling is especially important after the transfer of an embryo with a mosaic result. What screening and diagnostic tests in pregnancy can show, their limitations and possible risks should be discussed in detail.

Frequently Asked Questions About PGT and Advanced PGT

Decisions about genetic testing depend as much on the question being investigated as on the name of the test. It helps to bring any existing genetic reports and previous embryology results to your consultation.

Does a euploid embryo guarantee pregnancy?

No. A euploid result is a favourable finding for the chromosomes tested, but it does not guarantee implantation, an ongoing pregnancy or a healthy birth.

Does standard PGT-A always show whether an abnormality is maternal or paternal?

No. Determining parental origin requires an analysis designed for that purpose and, in most cases, additional samples from the parents.

Does Advanced PGT test for all genetic diseases?

No. Which changes can be assessed depends on the method used. If there is a known hereditary condition in the family, a specific test may need to be planned for it.

Does a mosaic result mean the embryo will definitely self-correct?

No. A mosaic result cannot reliably predict how the embryo will develop or how the pregnancy will turn out. A transfer decision requires a detailed assessment.

Can chromosomal abnormalities occur in IVF embryos?

Chromosomal abnormalities can occur in IVF embryos just as they do in naturally conceived pregnancies, and they become more common as maternal age increases. PGT can help provide information on this before transfer.

Is embryo biopsy harmful?

As with any procedure, embryo biopsy carries possible risks. These are kept to a minimum by an experienced team and suitable laboratory conditions, and are discussed in detail with the couple before testing.

What determines the cost of PGT?

The cost of PGT depends on the type of test, the number of embryos to be tested and whether additional analyses are performed as part of Advanced PGT. Exact information is provided after an initial assessment.

Is PGT covered by Turkish state IVF funding?

The scope and conditions of state funding in Turkey may change in line with current regulations. For details, please see our State Support for IVF page.

Is gender selection with PGT allowed in Turkey?

No. Under Turkish law, sex selection is not permitted without a medical reason. PGT is performed for medically necessary genetic assessments, not for the purpose of choosing the baby's sex.

PGT and Advanced Genetic Testing in Istanbul

At Dr. Soner Düzgüner's clinic in Istanbul, PGT and advanced genetic assessments are planned around each couple's medical history and existing findings. Where appropriate, parental-origin analysis and embryo–parent genetic match checks can be included in the treatment process.

For your consultation, you can share your previous genetic tests, embryology reports and any investigations related to pregnancy loss.